If you look into the momentum equation I had already talked about rate of change of momentum is consist of two terms unsteady term when you talk of rate of change of momentum inside the control volume and advection term when we talked about momentum change across the control volume. So the rate of change of momentum is equals to force. Now when you talk of force there are two types of forces like if you consider yourself as a fluid control volume and what are the different types of fluid forces acting on the surface of your body. There are two type of forces which acts in your body one is consider yourself as a fluid control volume one is the pressure which is directly proportional to your surface area and one is the weight which is directly proportional to your volume if you consider yourself to be a fluid. So there are these are the different types of body forces and the surface forces I will not go into much detail of it as I have to quickly go to the CFD part. So this surface force and body force you can resolve into components I would here like to point out that the way we had done the derivation this is what is called as the conservative form of the Navier-Stokes equation and in finite volume method we use this form of the we do not take the mass flux outside the derivative and this way we ensure that the mass conservation occurs to a very large extent. When you talk of surface forces right now I am here showing you the stresses let me tell you I am showing you okay so rate of change of momentum is equals to force. Now this force here what I will show you mainly are the two types of forces two types of surface forces which are there in all the fluid flow problems which are like viscous forces and pressure forces. Gravitational force in many a problem it is found to be negligible there are other forces which comes like surface tension force if you have two phase flow if you have electric field magnetic field other forces comes into picture but the viscous force and the pressure force are there in all the problems. So here I will discuss only these two forces what happens if you see a surface of the control volume the force may act in any some arbitrary direction here I am talking about the viscous forces the force may act in any arbitrary direction but here what we do is that we resolve into components because how we are doing balance as you do in let us say engineering mechanics course you do a three body diagram the force may act in any arbitrary direction but you resolve into component and then only you balance in fluid mechanics also we do the same thing there it was solid here it is fluid control volume. So we resolve into x component and y component so this force is expressed in terms of fluxes as stresses. So these are vertical phases so the surface area is delta y these are horizontal phases the surface area is delta x stress is a second order tensor and the first subscript here represents the plane in which it is acting and the second subscript represents the direction in which it is acting. Again you this surface forces it is a flux multiplied by area when you divide by volume you can easily get a differential term. Okay so in conduction you get del by del x of q x del by del y of q y in mass conservation you get del by del x of m x del by del y of sorry del by del x of m x plus del by del y of m y here you are getting del by del x of sigma xx plus del by del x of sorry del by del y of sigma yx note that this is stress in the x direction the x plane this is the stress in the x direction the y plane this is normal stress this is so you get sigma term in conduction you got get del dot q term here you are getting del dot sigma term in mass conservation you get del dot m m mass flux is a vector and as I said there is a subsidiary law like Fourier law of heat conduction to convert q x into as a function of temperature there is an expression to calculate mass flux in terms of velocity here also there is an expression to express this stresses in terms of velocities in pressure which is that law Newton's law viscosity actually this derivation professor Puranic had discussed in the previous lecture where he has used flow kinematics and shown you that stress is directly proportional to strain rates and strain rates is expressed in terms of velocity gradients that way expression between the stresses in solid stress is directly proportional to strain but in fluid it is directly proportional to strain rate finally I will show you the expression this is the final expression for stress as a function of velocity gradients sigma xx is minus p plus 2 mu del u by del x sigma by minus p plus 2 mu del v by del y sigma x y is mu del v by del x plus del u by del y so if you substitute this stresses in terms of velocity gradients by using subsidiary law you get the gradients so note that in case of mass flux and in case of momentum flux or enthalpy flux you were having the value of the variable at the phase center in case of conduction heat flux and here in this case of viscous stresses you get gradient of in conduction it is gradient of temperature here it is gradient of velocity this whatever CFD I am teaching is mostly restricted to incompressible flow that is what as a mechanical engineer most of the time we encounter and most of you I think are mechanical engineers so I had limited my lecture to incompressible flow incompressible flow we can further simplify this equation let me do how we can let me show how I can simplify so let me do one thing I will take out of this two I will take one of the del u by del x is that clear and out of this two term I will take one of the term which term I will take I will take this term and then I will show you that if you do a balance it becomes 0 how I will in the next slide out of the two if I take one and do a balance and divide by volume so if I take one means mu del u by del x x plus del x minus mu del u by del x x into delta y and out of this two term I take this term del v by del x at y plus delta y del v by del x at y if I do this what happens you get a term like this this becomes del square u by del x square this becomes del square v by del x del y if you take del by del x common what you get del u by del x plus del v by del y so finally I can express the stresses as this so instead of two time two gradient terms or two times of a gradient I get only one gradient for incompressible. Now I would say that this equation is very much similar to Fourier Laffitt conduction heat flux acts in which direction on any surface normal gradient which is involved in the Fourier Laffitt conduction is in which direction if you talk of surface normal direction in conduction q x is del t by del x where q x x in vertical surfaces. So in conduction heat flux is expressed in terms of normal gradient this is which plane x plane here is this which plane y plane plane is x and gradient here is expressed this gradient is referring to you will see that this gradient is referring to plane and what is the direction of the plane normal so here again you will see that the viscous stresses are expressed in terms of normal gradient of u velocity for x momentum equation normal gradient of similarly I can do for y momentum also I can take one of this two and let us say del u by del y and I can show that it cancels down to 0 and finally I can show that the viscous stresses in the y direction are expressed in terms of normal gradient of v velocity conduction heat flux normal gradient of temperature viscous stresses in the x direction normal gradient of u velocity viscous stresses in the y direction is the function of normal gradient of v velocity. So if you are developing code you will not write separate subroutine for conduction flux viscous stresses you will write one subroutine because for all of them you have to obtain normal gradient so you need to realize and appreciate the commonality in the derivation that is why I am doing the derivation fluid mechanics I am not yet started CFD in true sense these are some of the things which you should know understand and appreciate as far as fluid mechanics is concerned. You need to understand that there are fluxes the fluxes are at the phases this fluxes are expressed in terms of certain dependent variables some of this dependent variables are expressed some of this fluxes are dependent in terms of value of the dependent variables at the phases like mass flux momentum flux they are expressed in terms of velocities value not gradient there are certain other fluxes like conduction heat flux viscous stresses which are expressed in terms of normal gradient. This realization later on help us to understand and appreciate the discretization finite volume method in a better way. In conduction this is the way you do derivation I am showing you in one slide first you get this I called as first part of the derivation you are calculating total heat gain by conduction per unit volume this I called as the first stage of derivation then when you apply Fourier law of heat conduction which I show in the next slide this is the Fourier law of heat conduction then you can finally get the double derivative but here I again point out very specifically my slides are little detailed because I am not giving you lecture notes but I had written the important points wherever possible. So I have emphasized this normal gradient normal gradient of view velocity gives viscous stresses in the x direction normal gradient of view velocity gives viscous stress in y direction and normal gradient of temperature gives conduction heat fluxes. This diffusion again I can write all this viscous stresses and conduction heat fluxes this are basically what is called as diffusion phenomena. If you go to the transport mechanism they are basically occurring from random motion of the molecules. So physically the mechanism which gives rise to conduction heat transfer or the viscous stresses are due to random motion of the molecules. So this are called as diffusion term so this D is general diffusion term and this gamma phi is mu for dynamic viscosity for fluid flow and minus k for heat transfer problem and this eta is the surface normal. I am not showing you the normal direction the direction here why I am not showing you the direction here the reason is because this control volume I want to use for conduction when I use for conduction which direction the arrow points out surface normal q x q x plus d x q y q y plus they are always surface normal. When I want to use this control volume for viscous forces in the x direction then what happens on two surface it is normal vertical surface it is normal on horizontal surface it is tangential. So that is why because in a general proposition I am not showing you the arrows but the expression remains same. So the diffusion flux is viscous stresses this is viscous stress in x direction this is the viscous stress in the y direction note that here I had written two normal two shear on two surface it is normal on two surface it is shear and the conduction it is always normal conduction it fluxes are always normal here again I am not showing the arrow. So the total diffusion term if you do a balance it can be expressed as gamma phi del square phi this is k del square t in case of conduction in case of fluid flow this becomes mu del square u for x momentum for y momentum it becomes mu del square v. So that was all about although diffusion mechanism give rise not only to the viscous stresses but also causes pressure I am showing pressure separately for clarity. Now we talk about conduction heat transfer viscous forces and we talked about direction. Now let us talk about pressure where pressure act on a surface in which direction it acts non. So if I want to obtain pressure force acting in each direction on which of this surface I should draw pressure on the surface where the pressure acts in the horizontal direction because that will contribute the pressure force acting in the x direction. So I will only show it in the vertical phases I am not showing in the horizontal phase it is acting but just for derivation for clarity I am showing it only in the x because here I want my purpose is only to show force acting in the x direction again what is the flux term here what is small f here pressure and when I divide by volume note that here I get minus del p by del x because pressure is compressive and when I want to obtain net pressure force in the positive x direction it becomes p x minus p x plus del x become minus del p by del x this is the reason pressure you get as minus del p by del x. In fact in fluid mechanics class one of you were asking how it becomes minus del p by del x this is the derivation for that. Similarly if you this can be written in a vector form del p by del x as del p dot i where i is a unit vector in the x direction this is the pressure force in the y direction. So this completes the derivation this is the rate of change of x momentum per unit volume this is the rate of x momentum of the fluid inside the control volume note that word inside this is the rate of change of momentum flowing across the control volume rate of change of x momentum of the fluid flowing across the control volume this is due to Eulerian approach this is a temporal and this is an advective component this is equals to viscous force in x direction. Note that all the forces are in x direction viscous force in the x I am using subscript v here here it is not necessary because this does not consist contains any pressure term the normal stresses consist of pressure terms that is why I have used a subscript v to demarcate that this is viscous component. So this viscous this is the diffusion term this is the advection term this is the non-study term advection term diffusion term and then whatever remains in C of D language we call that as source term here source term is pressure gradient this is the x momentum equation similarly question is this is for incompressible or general right now it is for incompressible because I am using I had already used continuity equation as del u by del x plus del v by del y is equals to 0 when I was showing that when you balance the stresses out of the two term one cancels down. So there I had used an approximation of an incompressible flow so that way this is for incompressible this is for one momentum un-study advection diffusion and the source term similarly this is the energy equation rate of change of internal energy of the fluid inside the control volume rate of change of enthalpy of the fluid across the control volume total heat gain by conduction plus total heat gain by volumetric heat generation. There is a mistake here I am saying mathematically it does not come here it is a dot dot dot del dot is asking what is this there is a dot here so with this I come to the end of not this lecture session but the derivation because I have to complete this topic we will have 25 minutes before the T session but may be I will pause if you have some question I will be happy to answer till now I had shown you the derivation with the approach different from what force of pranic had shown you had shown you a mathematical approach I have shown you from control volume how to obtain why I am showing is that this understanding will help you to understand and absorb later on finite volume method which I will be discussing any question okay so final equation is this for incompressibility continuity x momentum y momentum as I said there is lot of commonality you can give to the student fill in the box type of problem this is what I commonly give I draw some boxes and tell them write down for x momentum y momentum equation there are two types of boxes one small box second a bigger box what is coming in the small box advected and diffused variable u velocity is coming in small box in x momentum v velocity is coming in small box and what is coming in big box minus del p by del x this small box finally when we talk of generality I will denote it as 5 and this big box I will denote as a source term s of y for energy equation actually this small box is not only temperature it is specific it multiplied by temperature and the big box is volumetric heat generation so this sorry so this is your final unsteady term advection term diffusion term and a source term from here real CFD start because from fluid mechanics we first propose that there is lot of commonality between momentum and energy transport we call that is the transport equation and once we realize that commonality then you develop one subroutine for this one subroutine for this and then use this for momentum as well as energy equation then this energy equation yeah I guess you assume that k is a constant yes yes his question is here I have assumed that k is constant in most of the cases indeed this is true however there are cases where heat transfer become non-linear when I will be taking conduction theory as well as lab we have different separate lab session for that I will discuss it separately but here this is the first course in CFD so that is why I am trying to make it simple as well as most of the commonly encountered fluid for heat transfer where k is constant more complicated situations we can take it later on we can discuss it separately okay so as I said that this is the just what I explained this is just like a notes you can see later on but before I end in CFD you should also understand and appreciate not only the different terms but the fluxes which is encountered well again emphasize in different slides what are the fluxes which you encounter because this is what I call as small f okay because this comes at the phase centers and then we need to use approximation in CFD so what is the flux which comes when you apply law of conservation of mass mass flux what is mass flux made up of normal velocity and the surface area and where this mass flux comes into the expression it not only comes in the continuity equation this mass flux also comes in the x momentum y momentum and energy equation where does it come because it acts like a driver where it acts in the advection term okay so note that this not only comes in the mass conservation but it also comes in the x momentum y momentum and energy equation to advect u velocity v velocity and temperature respectively the second flux in general is what I call as advection flux and what is this advection flux advection flux is made up of two variables one is called as advecting variable which is like a driver I said only mass flux and the second is advected variable which are velocities and temperature depending upon the equation so mass flux advection flux and then the third flux is diffusion flux okay so this fluxes comes at the phases and we need to use approximation to calculate this some of this fluxes are expressed in terms of value and some of them are expressed in terms of gradients so we need appropriate approximation whenever we do a CFD study especially as an let us say you are in academic institute and if you do a research or let us suppose you are doing a PhD normally it is suggested that you should follow standardize procedure is that you do a non-dimensional study okay later on when we will be giving you codes in the lab session we had made it non-dimensional we will be doing problem not only for isothermal flow but force convection mix convection natural convection so non-dimensionalization is an important concept in fluid mechanics so we do non-dimensionalize because in any problem we have certain non-dimensional variable like for flow in a pipe diameter of the pipe is taken as the non-dimensional length scale so when you do non-dimensionalization finally this is the dimensional form of the equation when you use a characteristic length scale and the characteristic velocity scale and you non-dimensional temperature for constant wall temperature in this manner and for constant heat flux in this manner finally you get a non-dimensional equation continuity x momentum and energy equation this I have written in a vector form I would like to mention that if it is a force convection problem then you do not have temperature in the momentum equation but if it is a mixed or natural convection problem you have a source term which is made up of temperature so in force convection there is a one-way coupling the flow does not depend upon temperature but in mixed and natural there is a two-way coupling in case of force convection you only have Reynolds number but in case of mixed convection you have Grasschef number in case of natural convection you have Rayleigh number as a non-dimensional governing parameter when you talk of properties there are two types of properties one is called as the fluid property and the second is called as the flow property fluid property is basically thermo physical property and the flow properties are the properties by which let us suppose you create movie in CFD which are velocities pressures temperature note that not only the movie of velocity pressures and temperature are good enough to understand fluid mechanics because fluid mechanics is very complicated phenomena even if you watch a movie of fluid mechanics you cannot understand it completely you need to create different types of movies you need to be clever enough to create different types of movies so there is vorticity plots also vorticity contours which we draw to understand the flow in a better manner there are different types of flow analysis tools which we use in CFD for to get a complete and although most of the problem let me tell you the flow are so complex that with certainty we find difficult to say that this is the reason for happening of something most of the time we feel because it is a highly very complicated so most of the time we need to write in research paper that probably this is the reason we make a statement that this is the reason reviewer mail reviewer will ask you that how you can most of the time although you may show some pictures and movies for confirmation but many times it is not confirmatory in a sense you need to be very conservative in your statement so when I talk of from the properties let us go to the parameters when we talk of parameters there are two types of parameters one is the governing parameter and second is what we call as the engineering parameter what is governing parameter when you do a non-dimensional study your results change if you change the governing parameter okay in CFD why if you look into the fluid mechanics problem why if you how the results change results change if you look into flow in a pipe or let us say flow across a car why the results are changing because the domains are different the shape of the domain is also different okay in a non-dimensional form when you do a non-dimensionalization these are the common governing parameter what I mean is that like for flow across a aeroplane you can study for when you vary the Reynolds number the results change this has the governing parameter these are the parameters which you vary which you play with and see the results so this is like an input parameter these are user input parameter and this is an output parameter okay this is an input parameter you vary this and then this results change this is called as engineering parameter non-dimensional form this is non-dimensional form of wall shear stress this is non-dimensional form of pressure drop this is non-dimensional form of drag force this is non-dimensional form of lift force this is non-dimensional form of frequency of unsteady flow this is non-dimensional form for heat transfer. Now, after non-dimensional the next thing would I would like to discuss is the initial and the boundary condition. Mathematicians have classified the boundary conditions into three types that is what I will discuss here. If you this is what type of equation and two dimension and steady state heat conduction with polymetric heat generation. So, there is one derivative with respect to time. So, you need one condition two derivatives in next direction two derivatives in y direction. So, two boundary conditions in x direction two boundary conditions in y direction. This is our governing equation in Cartesian coordinate system. So, we have to take a problem in Cartesian coordinate system. So, let us suppose there is a plate which is taken from a furnace. Let us say the plate is very long in the third direction. So, we are using it as a dimension. The length of the plate is l 1 in x direction l 2 in x direction. Now, to talk about the boundary conditions the initial condition will be let me take a general in the heat transfer we have three types of boundary condition. Let us say constant wall temperature insulated constant heat flux and convective boundary condition. Now, mathematicians have classified initial condition is let us suppose you took this plate from a furnace at temperature T 0 and then this is subjected to this boundary condition. Mathematicians have classified the boundary conditions into three types. One called as Dirichlet where the temperature is prescribed. Second Neumann where the gradient is prescribed. Third Robin or mixed where you have a linear combination of the temperature and the gradient. So, which one is Dirichlet of this four wall temperature boundary condition? Left wall is Dirichlet temperature specific. Which one is Neumann? Gradient is prescribed. Gradient is normal gradient of temperature is 0 here dT by dy is 0 and dT by dx is minus qw by k. So, these two are Neumann and at the top wall when you apply q conduction is used to q convection you get a linear combination of the temperature and its normal gradient. This is called as Robin or mixed type of boundary condition. Now, that was for a conduction problem. Now, let I had I show you one more boundary condition or initial conditions for external fluid mechanics problem. Let us suppose you have a cylinder. Cylinder is a common shape which you which we teach in let us say fluid mechanics or heat transfer. This is just for simplicity we take, but this can be an aeroplane or a car also. So, let us suppose we want to study free stream flow across a cylinder. So, you have you need one boundary inlet. As you know in fluid mechanics there are two types of problem. In general we classify out of two types external flow and internal flow. What is the size of the domain in case of external flow? Theoretically when you call external flow what do you mean by the size of the domain? Infinite domain size. But when you do simulation or when you want to create a pictures or movie of fluid mechanics you need some fixed region. The first question is what should be the where should this left wall should come? What should be the distance of this left wall of the boundary from the cylinder? This is very important question. So, you have to decide the position of the domain. Where should be? So, this is called as inlet. Why this is called as inlet? Because the flow is coming from this side. Why this is called as outlet? The flow is coming out from this side. This I call as inlet boundary. This I call as outlet boundary. This is bottom boundary. This is stop boundary. In CFD many times people use software like flow across a car and they take this boundary very close to the surface of the car. Why? Because they feel that most of the action happens near to the surface of the car. Let me take the boundary very close so that the number of grid points are less and I get quick solution. But is it correct? Because you should realize that the boundary conditions which we are using like this outlet boundary conditions which we are using. What is this boundary condition means? del u by del x equals to 0 means what? Flow has become fully developed. If you take this boundary very close just behind the surface of the car let us say whether the flow has become fully developed. But you may ask that how can I know because if the car is going with different velocity this distance may be different. Yes, you are right. What you have to do? That is why I say that go back to that Einstein statement. You have to show that u2 cull and you place this boundary here one simulation. Place this boundary here second simulation. Place this boundary further downstream third simulation. And if you show that this middle one as compared to first there is lot of difference in the when you see a result there are two types of result. Qualitative result like velocity pressure distribution. Quantitative results like in this problem lift force and drag force. Let us suppose the result changes a lot between this location and this location as compared to the downstream. Then this is what is called as domain length independent study or domain size independent study. So, you have to take this rectangular region in such a way that with further increase in the size of this rectangular region there is negligible change in the qualitative as well as quantitative results. On top and bottom wall although you may feel that on the top and bottom wall it should be u is equals to infinity v is equals to 0. But this boundary condition is better because even if your height is small this can give you an accurate result. This is called as a free slip boundary. Free slip is normal velocity is equals to 0 normal gradient of temperature velocity is equals to 0. This is a horizontal wall. This is a normal gradient of tangential velocity. Now, when I talked about the derivations the Navier-Stokes equation in a general form the non-dimensional flow properties fluid properties. Sir, excuse me sir. Sir, I got a doubt in initial and boundary conditions. Yeah. When I teach this. Thanks for correcting me. When I teach computational fluid dynamics to my students. Yeah. Place it on. If you talk about boundary condition initial condition you take a heat transfer conduction equation from a mathematical point of view I am able to tell for example if it is one dimensional unsteady. Please use my. Yeah. If it is one dimensional unsteady from mathematical governing equation I am able to tell that I need two boundary conditions one initial condition. Yeah. Like that Navier-Stokes equation will be able to generalize. Your question is. Boundary conditions for Navier-Stokes equation. Yeah. Yeah. From a mathematical point of view. We can generalize. Yeah. If you throw some light on that it will be better sir. Okay. Okay. When it at appropriate slides I will highlight that. Okay. Thank you sir. His question is basically I showed the boundary condition for temperature but the same thing can be done for Navier-Stokes equation also. Okay. Now, before I end this I would like to mention that once you get the results software what they do is that they call as post-processing because this results first you obtain in terms because first you obtain in terms of velocity, pressure, and temperature but if you show this movies let us say movie of flow or temperature to let us say industry they may not be that much interested. What they may be interested let us say car industry may be interested that how much petrol needs to be spent on let us say drag port which is exerted so that the car has to propel that drag flow. So they need parameters which we call as engineering parameters. Those engineering parameters are calculated using certain integral equations like drag force is calculated by taking the cyclic integral. There is a mistake here this is a cyclic integral. Cyclic integral if you take at the surface this is the surface normal this is the stress tensor and this is dot i. What is stress? This sigma is a second order stress tensor the dot product of a vector and a tensor is a vector and that vector if you take the ith component it gives you drag force and if you take the jth component it gives you lift force. So we do the surface integral and this is for total heat run. This all these integrals are done at the surface. You can also obtain this using an integral approach where you take a much larger size of the domain but here I am showing you surface integrals. Like if you have an inclined plate whose normal unit vector is expressed in terms of ai plus vj and this is a second order stress tensor. If you take the product of 2 you get a vector and if you take it is ith component you get the drag force and if you take the jth component lift force and this is the conduction if you take a flat plate and if the flow is on the both the sides then you can obtain the viscous stresses shear normal stresses and then finally calculate the drag force and lift force like this. I am not going into the detail actually the expression previous slide you can work it out. This is quite straightforward. So with this I have come to the end of the first lecture.


Hello. Good morning. Good afternoon. Hey Alex, are you there? I can't hear you. I'm here. Can you hear me now? Yep. Good morning. Good morning. Afternoon, I guess. Yeah. Just wait a couple more minutes and then we can start. I was hoping Sugu would be joining soon. Okay. I think we can start. So we have two documents that we wanted to review this time round. The first is the database paper that Sugu has been working on and the second is the project review process that Theron has been working on. Sugu, do you want to just give an update as to where we are on the database doc? I know that Quinton has put some feedback into the doc and I've just written up some some notes that I'd like to go through as well. Sure. Yeah. So initially I think there was some confusion about what the definition of a database is. I think many of the comments came from that. Initially, when I wrote the document first, I had categorized pure relational DB databases as well as the new SQL ones as relational. And there was no clear differentiation between the two. And I think some paragraphs were talking about the pure relational ones and some were talking about the new SQL ones. And that clarity was missing. And so I think now what I have done is actually clearly separated the two. It's talking about pure relational as one category and new SQL as the other category. New SQL is kind of slightly broad and they have a large variation in what they support. But I've tried to address them in a generic fashion. So that is one that's I believe that's the main change I had made in the document. Understood. Okay. And there was also you probably you were not there in our last discussion. No, I wasn't. I'm sorry. Yeah, there was a discussion about what is a database in general like Cassandra was considered as one whether it should be a database or not. I think it was borderline. So we decided to include it. But we already have a key value store section. And so maybe I'm thinking maybe we should talk about the fact that this line is blurring and some systems whatever get categorized as in both. Yeah. So I think that's a fair point. So I wrote some notes at the end of the document just because I couldn't find the right place to add the comments for it. So I think one of the things that we were discussing in the past was in the rest of the white paper we had kind of defined the attributes like you know performance and consistency and durability and whatever. And I think it's probably worth adding a paragraph or two around consistency and eventual consistency and things like that. And any other attributes that we consider as important for databases. So for example, one of the one of the other things that I talked about was do we need to discuss the topologies of the databases specifically in terms of things like consistency versus availability versus partition tolerance and things like that. I actually so the debate I'm having about it is those are generally considerations are not necessarily a cloud native concern. But I don't have an objection to adding it. I mean it's an important thing that people should think about when deploying databases. Yeah. I think we actually have a section in the white paper around sort of the cactus and you know in broad terms. But what I was thinking is that some of these some of these items you know we should discuss the attributes in terms of the different topologies or the different database architectures. So for example if you're if you're operating with a master slave type environment for example you have particular consistency and availability attributes. Whereas if you have a large-scale distributed system which is you know sharded or whatever else you know like like for tests or even you know things like spanner or whatever you have different consistency and different availability. Yeah yeah yeah I can I can there's there is actually the third there's a third property which is durability. So basically all these systems juggle with these three durability consistency and availability. Yeah so I mean in the previous in in sort of previous sections where we found these sort of things we even made just like a little table which kind of just said you know for these three types of topologies these are the relevant attributes that you should expect and it kind of helps to select sort of different usage patterns or you know different types or classes of database for different use cases. Sounds good yeah I have actually referenced that section in this thing it's section 9.4. Right yeah okay cool. Yeah I'm in favor of the table too and you know in terms of a table I think maybe you have to there are just so many potential databases that I don't think you can cover all of the dozens or maybe even a hundred that are out there. So first pigeonhole them with some popular examples in each category and then cover maybe in the table the topology differences the factors involving wanting to split if if this database is implemented by multiple nodes there often are going to be failure domain considerations and storage failure domain considerations that might be independent of the compute. So I think maybe covering that in table would be great. Well I think that's always dangerous even listing the popular ones I mean could we just figure out what the technical architectural differences are and separate them out and then have the list not lead with the popular examples but lead with the architect classes yeah yeah I agree with that it's just that having you know sometimes you could have a bunch of text and somewhere in there throwing a popular example might solidify it in somebody's mind if they're familiar with something. I don't want to be king makers here and nominate whatever examples we give as you know the foremost examples in the category though. So so that we don't rehash the debate from the white paper we kind of had we kind of had quite an extensive debate as to what we include and what we don't include in terms of project names or whatever else. We certainly said we should include we should include references to some popular examples that allow people to apply you know context to what they already know because that helps them understand the document. So for example it's kind of nuts to describe an object stored without mentioning this tree and it's kind of nuts to talk about the key values stored without talking about that cd for example especially where maybe some of those projects are cncf projects as well. So I think having a handful of examples is fine as because especially if they're sort of you know generic household names but I agree in general we're not aiming to be king makers here but where an example serves the purpose of clarifying the documents I think that's fine. Yeah I think I yeah I definitely agree with leading with architecture and and if for example if Spanner definitely is the leader in some others architectures so it may dare if something relevant to Spanner is mentioned there is no harm in talking about it. Yeah the one thing I'm wondering about is there is this concept of atomic clock that many of them use for a better serializable consistency Spanner that kind of is a big subject so I don't know if I'm wondering if we should even mention that. Well so so I think in a lot of these things right there is there is a question Marcus do you know do you consume this as a service do you do you build this you know and similarly for example we kind of said when we were discussing topologies in the white paper we said you know sharded systems are great at balancing out the load but one of the disadvantages is you know you have to you might have to have operational requirements to to rebalance workloads if you kind of get the shards wrong in the first place you know and those were like some of the pros and cons for each of the different topologies so I think it's completely fair to say that if you want a really big distributed scalable database and you want strong consistency and not eventual consistency then you know things like strict timekeeping are are a complexity factor and if you're considering it you know this isn't just like something you can you can ignore. Cool cool so I'll give it a shot I'll try to I'm thinking this is probably about two or three more paragraphs hopefully I'll try to constrain myself to about two or three paragraphs to see if I can cover all the trade-offs and then we can have another review of those parts. Yeah with regard to your comment about the clocks I'd say that certainly if the clock requirements for something are so tight that it presents difficulty in containerizing it then it needs to be mentioned. Oh yeah you're right yes yes we can't we can't necessarily expect clocks to be accurate in a cloud. Yeah that's a good point and then one sort of one other small point I had was you know do we want to do we want to discuss or include the paragraph for sort of caching layers and does you know does a cache like redis or whatever count as a database for example. Oh yeah redis and redis most definitely counts I mean it can be used as a cache but you certainly have the option of putting backing storage on it and I've encountered many instances where it's done so there's no doubt to me that redis is in the database category. I think redis is more a key value though. It is but the values are a form of database I mean etcd is a key value too. Yeah so that's the thing which I'm weird because we have already have a separate section for key value stores. I'm wondering may I'm even I thought maybe we should merge the two you know like because many of them are evolving into databases and databases are so many databases now start to give key value APIs. I mean honestly if that's the if that's the right call to kind of have one section which is called key value stores and databases and discuss them together that's probably fine. Yeah like Mongo just announced transactions so they're completely blurring now. Yeah and you know and we also have for example we have titanium kv the ti kv project which is used as a backing store for the ti db project and the ti kv is is already a cncf project anyway so so yeah if if you think it makes sense to merge that's not something I would be against. The question is should we iterate towards that right or should we go for the big bang and well it's probably easier to to stick to databases and then you know add in if we think that if we really think that they should be merged we can always do that as a second step but it's it's kind of up to you if you if you think it's too hard to to keep the separation then. So I think what I'll do is I will I will definitely mention that these lines are blurring and and that sometimes things can come in both categories I think that's important to mention and then maybe we can do another short at putting putting the two together and see how that looks as a separate attempt and then yeah that looks good we can merge that in. Yeah that probably makes sense. Cool so I have to so I have two two points one is to mention this that the lines are blurring the other one is the two or three paragraphs about the trade offs there was one more thing I think you say we needed to talk about. Oh and I also I also mentioned do you want to mention sort of proxies and load balancers or or things like that I don't know whether it's much of a factor or not. Actually I have a specific paragraph for that I am actually stating that a proxy is more or less a necessity to run in the cloud. Right yeah it's coincidentally Kelsey tweeted the same thing yesterday. Oh right well I know I know that for example you know things like Envoy for example are actually adding database protocol level sharding and things like that to the proxy layer so for example I know that they added support for MySQL and they added support for Redis and they actually do a bit of sharding themselves. Oh yeah so the section let me see the section is yeah the one where I had the comment says this is specific to MySQL and Postgres so we can maybe expand that out a little bit. I tried to not mention any specific proxies. I think it's fine to mention something like Envoy because it's a CNCF project anyway. So I will expand that out so I know I let me know time to start making notes. So I need to mention the lines are blurring I need to mention the three sections on three tradeoffs and proxies okay. Brilliant very cool. Thanks for all of this. Let me let's go through your comments make sure that they are all covered. Consistency and eventually we are going to cover that do we need to yes the second and first and second are a combined topic. No SQL and document databases for now we'll choose a category and put them there for now and then eventually we'll look at merging them. Cassandra I think last time we agreed that it should be in databases I think it's a clear example of a borderline case. Yeah cockroach strong consistency that goes back to the first and first two. Yep databases based on an underlying key value store. Yeah I think I cool I will I think that's a good good point we should fold that into the new SQL categories because that's where they are most relevant in memory databases and our caching layers so that we I think maybe I will add an edit for the for section nine to mention reddit and main cache. Okay so ready this already mentioned in section nine. Oh cool perfect awesome no need to change that use of proxies we have already added oh cloud provided databases that would be a can of worms because they are all commercial and there is actually like in the last year or so there's probably like hundred vendors that claim to be cloud provider databases including by the way planet scale we are about to announce our own cloud provider to be test database. Right okay all right so so maybe let's not get let's not open that particular kind of worms. Yeah so yeah I'm really afraid of that it's a very contentious subject I think that's that's fair enough. Cool cool all right so I will make this I'll try to make these edits within the next week or two and then let's have another go over this one. That's awesome all right should we move on to to erin stock in that case next. So the the the latest version of the doc is in the um meeting minutes agenda um have people found that or and the title should be cncf sandbox process template open and the reason for that is there were two docs one didn't have the proper permissions for people to comment I'll also put the link here in the chat just in case you can't find it in the agenda. Ah perfect thank you so yesterday I was uh invited last minute to the cncf closed session um to talk about the stock to the toc and they were brilliant extremely receptive and excited about this um they were gonna spend some time going through and adding comments um but they they fully agreed that yeah we we need a better well-defined deterministic process for people to understand um and how the sigs interact with the the toc long term so the it's still pretty rough but I wanted people to to weigh in and that didn't intend this to be a polished document by any means but just to solicit feedback and come up with a better process so the main points at the sea that the toc agreed on was time boxing that you know there should be a responsibility on the toc to review things within a timely manner and provide a response back um there should be a way that projects understand if they are rejected why they're rejected um and um you know with the possibility of like a re-review so that we talked about the toc saying like you know here's the criteria by which we're judging the it doesn't fit these things but we would re-review it in three to six month if these things are fixed or it's not cloud native you know by design and therefore it's rejected so I think they have a problem of not saying no and uh and or just letting things flail um because they don't want to say no and so I think that that has to stop so um and they also agreed we don't have a good process now for what the this responsibility is because I told them I feel like we end up with duplication now now we have sigs we review things we give them a recommendation and then the project still end up presenting um to the toc and we start over from scratch so how do we also make it a more efficient process makes sense to have the subject matter experts review the projects and do the due diligence and give a recommendation so um how do we do that better so I don't know Alex I don't know that we need to go through it line by line or if people just want to put their comments in and I can tell the toc that we have reviewed it as a sig and maybe give it to sig apps next and have them weigh in before we yeah definitely we can um I think we all should um I think we we should all review this so if I'm if I'm just looking at this um in terms of in terms of sections we're kind of defining what we expect out of the out of the toc and the process and the timeline and what also what the process in the sig itself should be right in terms of when they hand it over to us yes and the other thing that they were kind of knocking around that I think is worth noting yesterday on the call was having yet another level of entry into the cncf that's just for neutral ip to me that's what sandbox was supposed to be um so I just wanted to point that out it's under the project rejection recommendation project marinate and the linux foundation public group we're trying to find out what that level was there was no decision made on it but then they just talked about well maybe we we need somewhere that it just goes and and gets more contributions or fix you know fixes governance or etc and to me I always thought that's what's the intention of sandbox was so I think there's definitely still some uh cohesiveness that has to happen of what the expectations are at each one of these levels so it's it's good that we're talking with them about it I mean as we had previously discussed some of the challenges were having having sort of the this this perception that the goalposts were changing because maybe different criteria were getting applied to two different projects and I and I think having having this um having this process formalized will hopefully remove that that issue I'm not entirely convinced that we need something more than a sandbox honestly or something less than a sandbox person because I think the sandbox is kind of very intentionally broad I and I was a bit surprised by the suggestion um but just hoping that this helps because I told them my concern is one there's no time around any of these things key cloak that we propose has been in over a year waiting to be given a decision and to me that's not only has the entire TOC changed but it seems like the criteria by which their judge has changed right so things have to be time boxed and people have to understand the criteria which they're getting judged against because though I know they have good intentions then I think I hear these rumblings of unfairness right like well how come this project got in but my project didn't get in and why was it rejected and and and I think they also haven't been doing that in the public they they do it quietly in the background but that doesn't help other projects learn what they should be doing so I think that's that I think it's okay to say the project doesn't fit based on this criteria and have that be public information I don't think that needs to be done in private so I'm hoping there is more transparency that comes out of this yeah I think people may be concerned about once they know it they may game it so maybe we need to have a way to verify right yes and that that Joe beta brought that up like he doesn't want to have like a criteria and they say well I've met all these so then you have to accept me and I tried to make the language in there address things like that like these are the minimum viable criteria these are not the completeness of what it needs to to be you know I mean we it just needs to be worded in a way that gives the TOC the flexibility but it also gives a good enough direction for these projects so I don't know it's it's hopefully a step in the right direction I I I think it's definitely a step in the right direction I mean for for what it's worked my my two cents is that the sandbox is a great place where a project can mature and get and gain it's it's it's first few steps under the foundation right and I think a lot of the challenge and you know especially the comments about the gaming right is because the sandbox shouldn't be about marketing or or sort of gaining gaining commercial sort of plaudits or whatever from the CNCF because you're in the sandbox it should be about building up the community building up the governance and whatever else to get to the point where where you go get into incubating and I think the the the key thing that's missing here is that you know the guidelines around not marketing and keeping the sandbox projects as a separate category are really really important because a lot of the question marks that we kind of keep on keep keep on hitting around the moving old posts are because the sandbox projects then you know directly do get marketed and things like that so people do see the sandbox projects as getting the gain and I think that's that's a challenge here we if if there wasn't that perception of getting the gain and it was all about the community then um some of these issues would just go away well once you become sandbox project then by default you will have like a intro and deep dive session at cubecon where I think that's huge too so even if they say no marketing definitely once you become a sandbox project you get a lot of more traction yeah well that is true well and I agree and I it was unsettling to hear such diverse comments around sandbox in from the TOC board of what people thought it should be you know what I mean like I think some people have really high expectations of what they think a sandbox project should be whereas I have I feel like a long time ago we removed like the due diligence for sandbox for the exact reason that it could it could grow and flourish and expand the community there so I mean things like that have to be you know it has to be consistent for every single member on the board of what they expect or you know it's chaos yeah the the fact that like I think when they were discussing sandbox projects they were talking about like having like a hundred like accepting them in the hundreds which kind of which probably won't scale for these cubecon sick talks right if suddenly like a hundred of them want to present that's probably not going to work argumentially yeah yeah I agree so go free to add comments suggestions you can put it directly in the doc or add as a comment I I mean I don't I want it to be a community driven document I don't feel like necessarily need ownership of any of this I just would like to improve it for everyone I think we've certainly ran into some of these things you know just as one of being one of the new SIGs reviewing projects so your input is definitely desired so that's cool did you did you commit to having this sort of done by any particular date or having it handed off to the next segment by any particular date no they just it was like a last-minute thing hey can you join and talk about your doc and I said sure and then I didn't commit to dates or finalization they wanted some time to review I can bring that up on the next public call and we can figure out a date that we could drive ideally I think we would want it done by cubecon we would want to have this criteria set forth published and you know so new projects can look at adhering to that yeah I think that's a good goal to have that's a good goal to have okay that sounds good were there any other sort of specific points we wanted to discuss around this process I mean were there any you know particular process points that you wanted specific feedback on right now or or can we do this offline I'm fine with everyone just adding their comments offline okay so what I wanted to do next then is the the the last thing on the agenda is to discuss the the benchmarking and performance paper which I've only just started putting together I kind of want to apologize for letting this slip I was meant to set up a call a couple of weeks back and then life happened and it didn't quite happen as I planned so what I'd like to do just now is discuss some of the ideas and perhaps have a little bit of a brainstorm so that's I can put some an outline together and share with the with the group and then we can actually have a meeting to start sort of fleshing out some of the some of the details of this of this paper so in terms of in terms of scope for this paper what we wanted to kind of do was have a place where we can offer information on the tools and methods for measuring performance and and benchmarking the cloud native storage and what I wanted to specify as goals were going to be sort of the following three things the fine the commonly used tools and the and their test criteria the fine the the common pitfalls that that people come across and provides the ability for users to use these tools to measure their own environments specifically the non-goals so the things that we absolutely don't want to touch is we're not going to be publishing benchmark numbers and we're not going to be providing sort of our own vendor or product or project comparisons it's it's it's all about sort of providing the end user with the ability to run their own tests thoughts comments questions does that make sense um why would we not publish the benchmark numbers just curious um so so my take on this is benchmarks are very very often kind of how long is a piece of string sort of concept it is there are so many there are so many items that can affect a benchmark from the environments that you run it in the cpu the cloud instances the networking the actual physical storage how everything's interconnected how the storage is configured and everything like that that's actually providing numbers is generally very specific to a very specific environment and I think it's always kind of opening yourself up to to sort of being gained because it it kind of creates this environment where you know different people might want to publish different benchmarks and they tweak everything for a particular use case and I don't really want to get into that into that arena where we're having to argue the pros and cons or the how do you compare apples to apples between different benchmarks different numbers so what I'd really like to focus on is to give people the ability to run their own tests on their own environment so if they're if they're looking to test two projects in their or or two tools in their or two providers or service providers or two storage vendors in their Kubernetes cluster they can use um they can use the tools to to sort of compare them in their own environment as opposed to and and obviously what it allows them to do is for the end users to then actually publish their own numbers but that would be their numbers for their environment as opposed to our numbers in some hypothetical environment yeah and people cheat a lot they like turn off safety features of the databases to get better numbers and stuff well yeah I mean and and and this is why I said you know I kind of want to document common pitfalls so for example you know um storage systems will go faster if they're replicating with loose consistency or asynchronously rather than synchronously and you know they will perform amazingly if the entire dataset exists in cash and doesn't actually hitting you know physical media for example and things like that so these are things we can we can actually you know have a few paragraphs to actually document these things so people know what they're comparing but I don't really want to get into the into the complex scenarios of trying to justify why a particular system has a particular number because I think that's if if you know if promoting a particular project is a kind of worms describing the performance of a particular project is a gigantic kind of worms I'd agree with that I'd maybe even even if we give users the tools to run their own benchmarks and then publish them I'd even be go so far as to say maybe we'd be hesitant to publish links to those unless we're prepared to validate that the tests were done in a repeatable and provable fashion yeah absolutely I mean you know at the end of the day we don't want to become like an spc institute or whatever right to to to sort of have paid performance tests or something like that that's kind of not the scope of this this is this is more a case of we've written a paper and people understand the different aspects and different attributes of the storage system and what we're trying to do here is give them the capability of measuring one of the attributes which happens to be performance and we might you know that the next thing might well be something like consistency for example and we might suggest different tools to to test those kind of conditions but I don't want to actually be in the market of publishing the marketing numbers so to speak yeah I agree so the the summary is we're going to set ourselves up to teach people how to fish we're not going to catch fish for them and we're not going to run the fish mark basically yeah and so do we need to have a disclaimer that they can't also use those numbers to feed their own but like I don't at all disagree with the reasoning behind it but I also don't want it to be used as a weapon against other people saying using the benchmarks for their own purpose then I mean how will we prevent the other side of it even though we don't publish it how do we prevent other people from taking those numbers and doing comparisons and so are you saying you're afraid of something like some vendor puts out a press release saying we ran the official CNCF benchmark process and here's the numbers exactly um not that I would think anyone on this call all would ever do anything like that I'm just you know I don't want it to be used as a weapon against us that we're suddenly in the middle of well I think unless we made some attempt to ban people from making statements like that we can't stop them no but we could also have like before they use the tool they have to agree to that like these are not to be released for public this is just for personal use right you know we get some really strong legal disclaimer for the use of the tool before they even are allowed to access so so first off so a couple of things in in the first instance we're not building a tool or a framework we're describing tools which are publicly available anyway and most of those have some sort of disclaimers anyway of their own but but either way you know we're not saying we're not building a tool that somebody is going to use the CNCF storage tool or whatever right but also secondly I think the CNCF has fairly well documented things around trademarks and things like that you can't really use things like CNCF and the logo of the CNCF and all of those sort of things without the CNCF permission so I'm not I'm not too worried about that and the CNCF are actually pretty draconian at enforcing that as well yeah I agree and and the other thing in terms of stopping them from a legal perspective in the sense that you know we're pretty much on an open source license with that allows people to fork it will I don't see how since anything we'd produce would be under the open source license that people couldn't take whatever it is and declare that they had forked it therefore they can do whatever they want yeah yeah that's okay I just I just wanted to note my concern there but I think you guys are right there there should be framework in place and people decide to use it on their own anyways I mean I can't stop them from using open source stuff to justify things yeah so I guess we should talk about how to configure the tools and basically not how to configure the database that they are testing against right that's what it amounts to yeah exactly I mean mention that this benchmark tests this type of workload so make sure that your the workload that you intend to run in your production matches what the benchmark is trying to do that stuff was my plan and you know it all it also means that people can you know use the tools to benchmark different configurations so you know something like if they want to measure you know the query performance between having two replicas and three replicas for example you know they can also do that you know that that kind of thing so so initially what I was what I was thinking of doing was focusing on volumes and databases as two things to to measure I know that we could also potentially do key value stores but I don't have a ton of experience in that space unless somebody wants to help with that area but certainly you know in the in the volume space there are there are a number of good open source tools including you know like the obvious ones like a file where we can sort of document the different types of different types of of sort of benchmarking criteria and block sizes and random versus sequential and read write ratios and caching versus non caching and compressed versus uncompressed and dduped versus undduped and you know all of those you know obvious things which are which are fairly well understood and I think with with databases there's you know certainly quite a bit we can do with things like you know sysbench or something like that with key value stores perhaps there's the iscb benchmark suite which which is quite popular there but I would probably need a bit of help to to to structure that bit of the document so so what do you guys think about sort of focusing on volumes and databases as a first step yeah so we have we have ourselves run both sysbench and tpcc benchmarks and when I was at youtube we actually ran ycsb against vitas but those are kind of I don't know how much ycsb has evolved since then right yeah I mentioned that I could have the person who ran the benchmarks document about how it should be run sysbench is fairly straightforward you just point it at a database and then it runs its queries tpcc is more complicated and there's recent interest about tpcc benchmarks but for a long time nobody even talked about them are the tpcc benchmarks sort of publicly available or do you have to purchase some sort of license to use them oh it's a public standard and there are many implementations there's one actually there's actually a sysbench lua version so you can actually run tpcc using sysbench itself oh I did not I was not aware of that okay yeah Perkana published open source that project that's actually what we used for our tpcc so so nick I see I see you're on the call and I know that previously you had reached out to to say that you might be interested in helping out on this did you have any ideas on this well the only thing I was going to I was going to say I think I agree with what's been said so far it was just the section at the beginning with the commonly used tools and pitfalls um I wonder whether we also need to define the concepts and I think there was a reference to that but I wonder whether um you know in terms of latency what that really means spikes versus average latency uh throughput um and then you know even down do we need to go to the level of saying ssd right cliffs and that sort of impact or do we gloss over that yeah yeah so I mean so I mean that's that would be the sd right cliffs would be one of those things where I would suggest it would come under the common pitfalls so you know just because people run these sort of tests and and if they don't run them for long enough for example they they they kind of get to to see the cached version of the ssd and um and then it slows down over time um and and I guess you know that sort of thing also applies when you're benchmarking in the clouds because very often the client providers provide you with a certain number of IOPS for for a for a volume and then um you kind of run out of credits and it's it's almost similar to an ssd right cliff um so so yeah I think I think that's probably worth doing um so if we're if if we're kind of agreed on on some of these um concepts I could put a quick outline together um and then it would be really awesome if we could have maybe a um just a separate call for the people who are really interested in helping write some of the content to uh to get together and we could kind of split up the work if that makes sense so do we have a tentative list of tools that we want to cover I would I think we can get um a long way of the way there by using sort of covering FIO and and suspension potentially um unless anybody has sort of like an idea for a another killer tool but I think those two probably give us a lot of the things we're looking for day one cool um so in that case um I don't know if there's um a specific person you think we could work with um and and nick um is there is there a particular time we we could um we could sit down and and sort of kick off after I send out the outline sure yeah I will uh I I thought I might I vaguely remember asking you for your email to start a thread but I don't think I actually started it ah okay why don't I do that then I'll I'll ping I'll ping you guys an email and it's good and we'll start the thread that makes sense thank you and then I'll add the engineer that uh random edge marks for us fantastic that would be brilliant okay so that was the last thing on the agenda did anybody have any other um items that they wanted to cover today so there was a third document that we discussed uh which I'm trying to remember what it was I think it was uh how to run each system um the use case examples that uh that Luis was was working on right yeah oh yes that one yeah yeah um so Luis wasn't on the call or wasn't able to join today so so I didn't put it on the agenda but maybe we can discuss it next time sounds good yeah because because ideally we want that template ready for coupon as well yeah if at all possible anything else okay in that case I think we're done one's four minutes to spare thanks for joining everyone thanks everyone thanks Alex thank you here bye bye


Welcome to the session on 8086 system bus architecture where we are looking for maximum mode configurations. At the end of this session students will be able to describe the maximum mode operation of an 8086 based system. Let us see maximum mode 8086 system. The maximum mode is for medium to large size systems which often includes two or more than two processors. Again if you are looking in this mode there may be a more than one processor in the system configuration and the components in the system are same as minimum mode system. And here the processor derives the status signals to control signals using the status information. Now here we are observing the block diagram of maximum mode system bus configuration where the processor derives the status signal S2, S1 and S0 and our chief called bus controller derives the control signal using the status information. In the maximum mode there may be more than one processor for system configuration. The basic function of the bus controller chief 8288 is to derive control signals like read, write for memory and IO devices and DN, DTA, ABLICAR, ALI etcetera using the information made available by the processor on the status line and the bus controller chief has input lines S2, S1 and S0 and CLOP and the inputs to 8288 are driven by the CPU it derives the output ALI, DN, DTA, ABLICAR, memory write, then IO read, IO write, memory read. The AEN, IOB and CEN pins are specifically useful for multiprocessor system AEN and IOB are generally grounded and the CEN pin is usually tied to plus 5 volt. Now here in the pin diagram of 8086 if you observe the microprocessor 8086 is operated in a maximum mode by strapping its MN oblique MX pin to logic 0. A processor is in maximum mode configuration of 8086 when its MN oblique MX pin is grounded and the maximum mode defines pins 24 to 31 as follows. So a processor is in maximum mode configuration of 8086 when its MN oblique MX pin is grounded or logic 0. The maximum mode defines pins 24 to 31 out of that the very fast pin or the pins QS1, QS0. These two output signal reflects the status of the instruction queue. The status indicates the activity in the queue during the previous clock cycle. So if you are looking in the table the possible signals are 4. So as per the first signal 00 we can observe there is no any operation that means QE is idle for the 01 first byte of an opcode for 10 indicating that QE is empty and for 11 subsequent byte of an opcode. So the second one pin is S2, S1, S0 these three pins or we can say the status signals indicates the type of transfer to be take place during the current bus cycle. And also if you observe in the table the number of possibilities for the status signals are the 8, for the input 00 it indicates the status is interrupt acknowledge, for second one 001 it is IO read, third IO write, for 011 fourth that is halt, for 100 it is instruction phase, for 101 it is memory read, for 110 it is memory write and the last status signal for the possible input 111 it is inactive or passive. So such a 8 different signals or we can say the status are indicated by S0, S1 and S2. Now the next pin is lock this signal indicates that an instruction with a lock prefix is being executed and the bus is not to be used by another post processor.  So there are the two different pins RQ 0, GT 0 and RQ 1 and GT 1. So in the maximum mode configuration of 8086 hold and HLDA pins are replaced by this request and grant kind of signal. So by using bus request signal another master can request for the system bus and processor communicate that the request is granted to the requesting master by using the grant. Both signal are similar except the RQ 0, GT 0 has a higher priority than RQ 1, GT 1. Here you have a question which bus controller is used in maximum mode configuration of 8086. So please take a pause and write your answer. Your answer is 8288 bus controller is used to provide the signal eliminated from the 8086 by the maximum mode operation. Here you can observe the timing diagram of the memory or IO read cycle without any weight state in a maximum mode of 8086 system. So in figure the status beats S0, S1, S2 are set just prior to the beginning of the bus cycle upon detecting a change from the passive state. The 8288 output upholst on its GT oblique R pin during T1 in T2 the 8288 sets DN equals to 1 thus enabling the trans receiver for memory read operation. It activates memory read cycle also which is maintained until the end of the clock period T4 similar to the memory read cycle which performing the IO read cycle. The control signal IORC is activated instead of memory read cycle the same way. We can observe the timing diagram for the memory write cycle without any weight state for the maximum mode 8086 system. So in figure for a memory write operation memory write is activated from T2 to T4 and memory write is activated from T3 to T4 the status beats S0, S1, S2 remains active until the end of T3 and become passive during T3 to T4. As with the minimum mode if the ready input of the 8086 is not activated before the beginning of T3 and weight states are inserted between T3 and T4. Similar to the memory write cycle while performing the IO write cycle the control signals of IOWC and AIOWC are activated instead of AMWC and memory write or MWTC respectively. And these are my references which I used for our slides. Thank you.


So, bonjour Dr. Tremblay, we just came off of your session on the fourth Hieny Summit on the health effect of yogurt consumption, that was very an amazing presentation that you just gave, so I have three little questions for you, so can you explain us what is healthy lifestyle in general? Healthy lifestyle is a lifestyle that fits with the health of people, so that contributes to prevent disease that includes healthy life practices, also for metabolic fitness, physical fitness and global well-being. So, Angelou, as a registered dietitian you know that I often recommend yogurt to my clients, but because it's nutrient dense, but can you tell me what is the most ignored fact about yogurt? One factor that we need to talk more about it is the status of fermented food for yogurt. The bacteria of yogurt are probably influencing the gut microflora, our microbiota, with consequences on metabolic health, which are generally considered as benefits, so we will learn more about that and we will probably get good news about this specific issue. And beyond nutrition, can you explain what does yogurt have to do with healthy lifestyle? Maybe it has a symbolic aspect also that makes yogurt being related to a global healthy lifestyle, including the fact that the yogurt consumers seems to be a more physically active person. There are also data showing that yogurt consumers are less likely to be smokers, so it seems that yogurt consumers live a little bit differently and it is for the best rather than for the worst. So thank you very much Dr. Trebley. Thank you. See you soon.


What's up everybody Jason for Jaspys case breaks calm. We just sold out the Jaspys high roller mystery crate Random hit number two. This is a seven-spotter and yes, it is not a typo guys This is a three thousand dollar hit crate spot But there are some amazing hits in here guys and the beauty of this is that everybody is guaranteed something So the way this works is first seven spots are sold guys We first open up the crate and show all seven cards or boxes And again Then what we'll do is we'll randomize the list of customer names and the hits Whatever you match up with is what you get and in every crate guys It could be either boxes packs cases break credit credit cards autographs all that good stuff But like I told you guys are this one is all cards. So Here we go. Good luck. So again here the customer names So PJ Ryan Brian William Blair bought these straight up and Blair got last Bob Mojo And then PJ won that in optic 25, but want to spot an angel just right now won an optic 26 Here you go guys. So I know it's kind of hard to see the crate But there you go without those keys guys. This is indestructible. You cannot get anything out of this crate without these keys All right guys, so again the first card I'm gonna show you guys is the preview card that I showed you earlier. It is a 2009 tops triple threads football autograph relics combos CPia Which is Tom Brady Patch auto Joe Montana patch autograph and Terry Bradshaw patch autograph It is a gem plus which everything all the sub grades centering was a 10 edges 9 5 corners 9 5 surface 9 5 for whopping 9 5 and it's game worn The only thing I think the autograph was a 9 and I think it's only probably because of Terry brachels But don't worry about that. This is what you want because the card is in perfect condition Gem mint gem in plus and it is all game used Embedded in this premium cards are authentic game-worn Jersey relics and Three top certified autograph relics and it is serial number 11 out of 12 So that was your preview card right there and that is one of the top hits though for sure That is a monster. I'll leave that one up right there Next one We have from eminence basketball, it is a diamond autograph of Stefan Curry 2017 all-star game six out of ten and you guys know how great a great of a year. He had this year Dude balled out wasn't for him and borders would be like a lottery pick right now So there you go Appreciate it right. That was a good one right there. Thank you Nick for adding this Steph Curry into this crate It's pretty nice next one we got is A 2018 Panini select it is LeBron James. It is a die cut tie-dye PSA 10 You know how hard it's a great tie Die cuts and it's first year LeBron James Laker Jersey and it's a PSA 10 serial number 13 out of 25 That is a big one right there two guys may not seem flashy or anything like that But it is a very very nice one right there PSA 10 as well next one We have a 2020 Panini mosaic football 9510 rookie autographs of Justin Herbert's Very beautiful card right here 9510 Herbie and you know his stuff's gonna go up as the football season approaches people are high on her But people are high on the charges in general So that is a very nice one right there All right guys, we're gonna start getting pretty wild. All right, I'll let you guys know 2018 Panini encased Vaulted veterans is actually only a second year in the league Or actually his first year as a as a as a starter the second year in the league, right? It is a bgs 9 Patrick Mahomes Inscribed chiefs kingdom and it's a two-color patch. It's a little bit of the yellow right there and 8 out of 10 bgs 9 10 This is from encased football Inscribed chiefs kingdom. This is his first year as a starter MVP or two little patty Mahomes That is a big one there All right you guys here we go last two 2019-20 Panini obsidian soccer It is an electric etch yellow Numbered to seven and it graded a nine five ten of Lionel Messi Whoo, this is a huge card guys Three out of seven Look at that beauty Someone's gonna get this nine five ten as well three out of seven definitely probably a Lot Brian. I don't know. I mean first of all, this is the number to seven So I have no idea. This is probably a really tough hit to get in a spideon and the fact that it graded a nine five ten to Sure, well worth the spot price. Lionel Messi stuff sells extremely well. Alrighty guys last one No baseball you're calling a trout bowman chrome rookie probably not, but I think for basketball fans This will be as good as it gets right now This is a 2012-13 National Treasures basketball. It is 11 versus 12 Silver signatures Zeroed number to 20 and it graded a nine five and It is a dual autograph Kyrie Irving and Anthony Davis and remember the double draft class. This is a rookie Anthony Davis and Kyrie Irving and It's number 12 out of 25 man. This is a monster she's Kyrie Irving Anthony Davis rookie 2012-13 National Treasures basketball Nine five ten You don't really see these too often For you will and yes messy, but not for everybody I Think there's a handful of people would still want this to people forgot about this one This was a preview card The last three hits were monsters and then you have this card you're hiding in there as well So there's a triple autograph Brady Montana and Terry Bradshaw nine five nine You have the nine five Ten Kyrie Irving Anthony Davis dual autograph from NT basketball. It's a rookie year You have messy number to seven nine five ten You have the Patty Mahomes number to ten. That's a BGS nine ten Chiefs kingdom inscription Justin Herbert nine five ten mosaic rookie autograph. You have a BGS ten. This one's actually really slept on though LeBron James Dykut tie-dye at a 25 to ten and then Steph Curry six out of ten Eminence basketball diamond autograph So let's quickly actually input these hits into the randomizer and then we'll see what you guys get So there's the customer names there There's that but at the end of the day guys everybody is going to be walking away with a Beautiful beautiful hit though. I think regardless Triple Thrust just 2009 pretty much says it right there 19 20 I probably go like the three legend quarterbacks Although, I mean the message is great. I mean internationally was like you say about if I'm strictly just besides value I mean, I think I think the triple autographs great But the message great, I mean I probably it'd be a toss up to me between the Anthony Davis Kyrie and the triple autograph to be honest That would probably be the tiebreakers for me like those two, but yeah, they're all I mean That Patty Mahomes is easily three thousand. I mean it really is it's crazy to say that but it is A lot of these hits are well worth the spot price. Some of them are gonna be over it Some of them would be exactly at it and some of them will probably be a little under three thousand But I guarantee you I mean the names that are in here The only one that really has the potential to fall in a way Is what maybe Justin Herbert, but then again everyone's thinking that Justin Herbert's gonna be The next Patrick Mahomes, right? Everyone thinks that's what he's gonna be You have an amazing second year MVP here may be charged with the playoffs But we just don't know that yet Patrick Mahomes, even though he's only like in his fourth year He's already established himself Anthony Davis Kyrie they've established themselves in the NBA Lionel Messi is a goat The triple autographs a goat, you know, Steph Curry is a goat LeBron James a goat I mean, that's the only one really that like is just kind of the risk in all these but it's still probably sells Extremely well as the Herbert. All right, so that should be one two three four five six seven. Oh, wait, did I do it wrong? No, okay What up Joe Pizzle? All right guys, so good luck good good luck Roll the dice. You got ourselves a one and a six for lucky number seven There was seven spots seven customer names seven hits. We're gonna randomize the seven times and see what you match up with guys Good luck one Two three four five six seven Seven times PJ down to Ryan Smith seven times guys. Good luck One two three four five six seven Boom Seven times obsidian soccer Lionel Messi three out of seven BGS nine five ten at the top all the way down 2018 in case Patty Mahon's patch autograph six out of ten BGS nine ten I don't know if you wanted the bigger stuff potentially, but although the Patty Mahon's pace for itself, but you got your boy Look at that, man So PJ congratulations, man. You got the obsidian soccer Lionel Messi three out of seven BGS nine five ten William with the 2009 Brady Montana Bradshaw triple relic plus autograph zero number 11 out of 12 BGS nine five nine Andrew from your free spot in the optic filler 2019-20 Eminence basketball Stephen Curry diamond autograph six out of ten Brian you have the 2012-13 National Treasures basketball Kyrie Irving Anthony Davis dual autograph zero number 12 out of 25 BGS nine five ten Blair last spot mojo with the 2020 mosaic Justin Herbert autograph nine five ten PJ getting the 1819 select LeBron James.   There was that dual autograph Kyrie Anthony Davis. That's a rookie year two nine five ten LeBron James tie die select PSA 10 out of 25 Lionel Messi nine five ten out of seven That is a big hit right there. There's that patty Mahon's chiefs kingdom inscription Two color patches a little bit of yellow right there Eight out of ten BGS nine ten. There's that Herbert nine five ten Steph Curry six out of ten diamond autograph and the triple autograph triple patch auto Brady Montana and Bradshaw nine five nine So again guys appreciated. This was the mystery crate on Jasper's case breaks calm Hopefully we'll have more next Sunday Monday. Have a great night guys