MadSci Network: Computer Science

Re: what is the fastest and cheapest modern processor?

Date: Thu Sep 23 12:08:54 1999
Posted By: Mike Westerfield, Staff, Computer Science, Byte Works, Inc.
Area of science: Computer Science
ID: 937764360.Cs

Reply From: Mike Westerfield
            Byte Works, Inc.

Your question seems simple on the surface, but it's sort of like asking 
"What's the fastest, cheapest car?" Like a car, faster generally means more 
expensive when you talk about computers. Also like a car, fast means 
different things. A car built for drag racing would get killed in the 
Indianapolis 500, and both a drag racer and an Indy 500 race car would be 
slower than the family van getting to the grocery store because there is so 
much involved in getting them going!

Computers are the same. If your task is sorting census data for the upcoming 
U.S. census, you need a computer that is very fast at simple logical 
operations and comparing values. As we'll see in a moment, the best computer 
for that task won't be the same one as the best computer for complex filters 
in PhotoShop. In fact, the only reliable way to tell which computer will be 
fastest for a particular job is to try that job on each computer. That's 
what benchmarks do.

The Spec Benchmarks

In general, there are two kinds of speed we measure on computers, integer 
math and logic, and floating point. The most common benchmark for integer 
math and logic is the Spec Int 95 benchmark, which is actually made up of 
several programs. The final grade is a number, and the bigger the number the 
better the processor did. The Spec Int 95 benchmark gives you a good idea 
how a processor will do on jobs like the U.S. census.

Floating-point speed is measured by the Spec FP 95 benchmark. Just like the 
Spec Int 95 benchmarks, this is really a group of programs, and a bigger 
number is better.  This benchmark gives you an idea how a processor will do 
on jobs like PhotoShop filters, spreadsheets, or predicting hurricanes.

Rating a Few Common Processors

Here's a table showing a few common modern microprocessors, along with their 
Spec benchmarks and a rough estimate of price. If the table seems messed up, 
change the font to a monospaced font like Courier.

Chip        Speed (MHz)     Price      Spec Int     Spec FP
Pentium III 450             $183       18.7         13.7
Pentium III 600             $869       24.9 (est)   18.3 (est)
Pentium II  450             $183       18.5         11.9
PowerPC G4  450             $355       21.4         20.4
Celeron     500             $204       17.9         12.9
Alpha 21164 533                        16.1         22.5

Looking at this chart, you can see how much you pay for speed. The Pentium 
III at 600 MHz costs almost 5 times as much as one running at 450 MHz, but 
only runs about 1.3 times as fast!

You can also start to see through some of the hype surrounding processor 
speed. The makers of the Alpha 21164 claim it's the fastest chip going--and 
for floating-point calculations, they have some support for their claim. But 
most people don't do floating-point, and look at how it does on the more 
common integer operations!

The Chip Isn't the Whole Story

For most applications, there is a lot more going on than the processor 
speed. Comparing two computers isn't the same thing as comparing the 
processors inside the computers! It doesn't matter much how fast the 
processor is if your job is copying files from one disk to another--it's the 
speed of the disks that matter. A lot of the time you spend on a computer 
depends more on the speed of your disk drives and modem than on the 

Making it Cheaper

If you're going to build something yourself, maybe a home-brew robot, there 
are lots of ways to make your computer cheaper. The modern processors you 
see in the chart are big, expensive chips. A robot wouldn't need them. In 
fact, you can probably get the microprocessor for free! As just one example, 
a lot of school closets are full of old Apple II computers that are being 
thrown away. Pull the 6502 microprocessor out and use it in your project, 
and you have a very reasonable microprocessor for the task for nothing.

Even if you need to buy a microprocessor, there are all sorts of specialized 
chips that cost lots less than the ones in the table. Some are rip-offs of 
the Pentium that run a little slower. Some, like the BASIC Stamp, are 
complete computers on a chip, designed for projects like building a Robot.

Making it Faster

If you're NASA, trying to build a faster computer to simulate air flowing 
over an airplane wing, there is another way to make your computer faster. 
Instead of using one microprocessor, why not use two? Or four? Or 1,024? 
That's called parallel computing, and it's exactly what big government 
agencies do. They build specialized computers that are really more than one 
computer inside, and program the machine so all of the computers work on 
different parts of the same problem. Parallel computing is expensive, but 
very fast. Sandia National Laboratories did the race car equivalent of 
breaking the sound barrier last year using a parallel computer when they 
broke the terraFLOPS barrier. Their computer did a little over 
1,000,000,000,000 floating-point operations in one second!

Another way to get lots of speed is by adding an extra processor for doing 
specialized calculations. That's what Apple did in their new PowerMac G4. 
Their microprocessor is impressive on its own, outrunning the best Windows 
based machines, but it's not three times faster like Apple's ads claim. The 
way they got the extra speed was by adding a vector processor, which is a 
special microprocessor that does some kinds of calculations blindingly fast. 
It really won't do much for sorting a database, but if you are using 
PhotoShop or doing scientific calculations, it screams. Apple claims that on 
problems like those, the new computer does 1,000,000,000 floating point 
operations per second--and it can go even faster in some cases.

Times are Changing

The speed you see today will seem slow when you graduate from High School. 
When I was in college, mumble-mumble years ago, the Cray 1 was the speed 
king. It was a big, expensive computer that needed a room, special liquid 
coolant, and a staff of people to keep it going. It's speed was about 
100,000,000 floating-point operations per second. It seems pretty slow these 


So, Joe, as you see, your question wasn't as simple as you thought! If you 
want speed, you have to shell out lots of money. There are different kinds 
of speed, too, so you need to be careful to choose the machine that is fast 
the way it matters to you. And if cost is more important than speed, there 
are lots of ways to cheat the system, sometimes so much that you get your 
microprocessor for free.


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