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bios battery

What is the bios battery - why is it important what does it do how do you change it why does it need changing!??

Ok lets start at the very beginning - The Bios is in fact a little program that lives on a little chip on the mother board. It is a very important and vital chip that is very important to the PC's functioning. When You PC boots or starts, the bios is the little program that is going to find virtually all the hardware in the computer, and of course it stores the time and the date as well. The bios Battery is a small battery on the mother board that keeps the bios alive when the computer is off. Often it is a small 3 volt lithum battery like a CR 2032, but there are many types some are coin type like the one already mentioned, some are larger than this coin type battery, like a small disposable battery. On some mother boards the bios battery is soldered on to the mother board, but on many mother boards the bios battery is not soldered on to the mother board and can be removed and replaced with nothing more than a couple of very small screwdrivers. Look if you are going to replace the bios battery , you need to take a close look at the battery before you remove it, note down on a piece of paper which way up the battery is, i.e. is it the positive end that you can see or the negative one, make sure that when you install the new battery, that you install it exactly the same way up as the old one that was in the board originally. This is importantant, installing it the wrong way round may damage the bios and or the entire motherboad for good!!?

Common Symptoms of the bios battery being week or exhasted: If you boot the pc and you see a black screen and it says Bios Checksum error, thats a good clue, or you boot the machine and instead of starting the operating system you find it does not do so and when you go into the bios you find out that the date and time is not correct. You then set the time and date to be correct save the settings to the bios and restart the machine but it still can not boot and the time and date you just set has been lost again and has gone back to 1st Jan 1980 or some such daft date. Look if you keep resetting the time and date in the bios and it keeps loosing it, then the bios battery probably needs changing.

You can of course measure the open circuit voltage across the battery with a volt meter if it is significantly less than the voltage written on the battery itself then this confirms the battery needs replacing. If you think about it for a while the bios battery must be charged by the electonics on the mother board, there is no way a little battery can provide power to the bios for years with out being charged, but it is oftern the case that an old bios battery gets less good at retaining the charge. It is of course possible that the circuit that charges the bios battery can of course go faulty, but this is less common!!

ATA 33 and ATA 66 and IDE Cables

The hard ware guru mutterings about Cables to connect you hard drives:  So is there a diffrence between ata 33 and ata 66, yes there is.If you look at an ata 66 cable  you oftern see a blue end and a grey centre connector and a black connector on the other end. Also, if you look at an ata 66 cable you see on the connector, which has on blocked hole on it, from the side where there is the red wire count ten along the bottom row and you see a blocked hole on the connector. This of course is diffrent on an ata 33 cable, where this wires particular hole in the connector is not blocked.

The next thing I'm going to say is going to appear plan bonkers,,,,,,  Although a  new 40 pin  80 conductor cable cable is requied to for ultra  ATA/66 the system  board chip conector ( or ide connector) remains the same having 40 pins. Or if you want to look at this in a practicle way, the ATA 66 cable is thinner than the ATA 33 cable, and if you see the two side by side this is obvious. In order to use ATA 66 you must have a bios on the motherboard that does support ATA 66, so check the specifications of the motherboard, eg A Bit AN7, so if we look at the spec amoungst the details for the FSB Front Side Bus and the socket type and many other details we see  Internal  I/O Controllers  2 X Ultra DMA 33/66/100/133 Connectors. These are the connectors for the ATA or IDE Disk drives. see this page for the spec AN7 System Board Specification

Back to the ATA66 cable. As I said there are oftern three coloured connectors, the black connector should be plugged in to the Mother board, the blue end into the primary drive and the grey connector into the secondary drive. The ATA 66 cable and drive is able to consitantly out perform its ATA 33 counterpart and transfer rates to and from the disk are faster.

Say you buy a Segate Barracuda 7200.9 disk ST3802110A, This is an ultra ATA interface or as it says on segates web site it is an Ultra ATA/100 interface. Notice This range of drives comes in a range of sizes, but it is the Ultra ATA/100 Interface that spcifies the actual connection to the cable.

Ok so what is Ultra ATA/100, the short answer is it is the marketing term for hard disks that use the Ultra DMA mode 5, supporting interface transfers of 100Mbs What is Ultra DMA mode 5, well it is one of seversl Direct Memory Access Modes. Of course a disks get faster and faster there is always a bottle neck somewhere, or in simple terms a place where things have to slow down to a speed that is constrained by something, either the physical cable, the speed of The spindle of the drive, the speed of accessing the DMA etc etc. The IDE Interface and the flat cable used for it was designed originally for a speed of about 5MB/sec, increasing the speed of the interface by reducing the clock cycle always cassed problems instead diffrent types of DMA transfer modes were born! super ahhey. there a 5 modes, mode 0 through to 5, and each one is faster that the previous one. To cut to the chase, and avoid a load of mind blowing technical wibble wabble, Ultra ATA /100 can be effectively understood to mean Ultra DMA Mode 5. That it really!?. accept to say that certain mother boards that are older do not function well when an Ultra ATA/100 drive is attached to them!!!



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