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Why AMD's PR rating is still working

Last response: in CPUs
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April 12, 2002 3:56:04 PM

This is my hypothesis:

AMD's L2 cache is design is more efficient than Intel and so it minimizes cache misses. This reduces the number of lost cycles when accessing main RAM, and makes AMD's processors less reliant on RAM speed. That would allow AMD's performance to increase more linearly per frequency boost as opposed to Intel or even AMD's previous T-Bird. If that is the case, then the PR rating is not flawed and should continue to provide an accurate impression of performance for some time to come.

Think of it this way. Intel (or AMD's T-Bird) increases clock speed by 10% and gets a 5% effective boost in overall performance. AMD increases clock speed by 10% and gets an 8% effective boost in overall performance.

AMD technology + Intel technology = Intel/AMD Pentathlon IV; the <b>ULTIMATE</b> PC processor

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April 12, 2002 4:14:48 PM

Have you ever visited Ace's Hardware? Great site, they really dig down into the products they review. You should be able to find L2 comparisons between the Athlon and P4 that show the P4's L2 cache having both lower latency and greater bandwidth. And we all know that the P4's data prefetch is more intelligent than the Athlon's (almost certainly because the Athlon's was added almost as an afterthought).

<font color=blue>If you don't buy Windows, then the terrorists have already won!</font color=blue> - Microsoft
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April 12, 2002 5:02:15 PM

I wouldn't trust that because of the date, especially since there is evidence that Intel improved the L2 cache as well as increasing the size when they made Northwood. I don't remember where I saw the test results, though.

<font color=blue>If you don't buy Windows, then the terrorists have already won!</font color=blue> - Microsoft
April 12, 2002 7:38:55 PM

Bandwidth is secondary according to AMD because the processor won't make use of most of the extra bandwidth a 256-bit cache would offer. If the L2 isn't what's keeping AMD together then it's probably the L1 cache. Something is obivously making AMD processor scale better in performance for each frequency boost while the P4 starts to starve for Main memory bandwidth at the mid-2GHz range. Of course, even with better cache implementation or at least more effective cache, AMD can't stay with a 266MHz FSB forever.

AMD technology + Intel technology = Intel/AMD Pentathlon IV; the <b>ULTIMATE</b> PC processor
April 12, 2002 7:54:13 PM

Well hey, you've seen the results of DDR400 and 400MHZ FSB memory on Athlons, and it does kick ass!
But you have to get this first: PR is either messy or very accurate. At times, it is very useful and is true, at others, it's very inaccurate and uneeded, like this for example: An app that uses SSE, which Palomino has, will not mean that a 1.6GHZ Tbird would do the same job than a 1.4GHZ Palomino, as it would probably take more MHZ for the Tbird to do the same as a Palomino SSE enabled. So this is one reason why the PR won't always work. This is of course the same analogy for MHZ itself: At most times, especially with P4, apps won't perform as good per clock, but when other times, apps depend purely on raw MHZ, such as Internet Content Creation, and thus the P4 easily wins them, as it has the MHZ advantage. Both measures are flawed, but each is also accurate in its own.

--
For the first time, Hookers are hooked on Phonics!!
April 12, 2002 8:19:20 PM

The most important reason that Athlon is more memory efficient is that the pipeline is shorter - pipeline branch mis-predictions require a reload of the entire pipeline before any useful work can be completed. Because P4's is longer, it can take significantly longer to reload. That is why MHz is so important to it and why more cache helps the NW so much. Cache becomes extremely important for reloading the pipeline - Athlon's is shorter, so less cache and overall memory bandwidth is needed.

I thought a thought, but the thought I thought wasn't the thought I thought I had thought.
April 12, 2002 9:49:41 PM

1 of many reason
Like this also the reason why it run at a high speed.

cheap, cheap. Think cheap, and you'll always be cheap.AMD version of semi conducteur industrie
!