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Subject: Re: A Strange Result, A P-IV at 1.7 Ghz Outperforms an Athlon at I.4 Ghz!

Author: Terry McCracken

Date: 21:04:50 01/20/02

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On January 20, 2002 at 23:43:21, Vincent Diepeveen wrote:

>On January 20, 2002 at 22:02:10, Terry McCracken wrote:
>
>>Can anyone explain how and why a P-IV at 1.7 Ghz with 512MB (PC800) RDRAM
>>outperformed an Athlon running at 1.4 Ghz with 266Mgh DDR Bus and 256MB of SDRAM
>>on a Fritzmark by a wide margin?
>
>fritz might be in p3 assembly and has probably nearly no mispredicted
>branches somehow. further it is such a small program that it hardly
>needs data cache.
>
I'm not sure what you mean that Fritz is a small programme compared to other
chess software? If that is so, then why is Fritz at the head of it's class
compared to other commercial programmes most of the time wich you say need more
cache and are larger programmes?

>The 3 major disadvantages from the P4 are
>  a) HUGE branch misprediction penalty
>  b) very SMALL datacache
>  c) no way to do 4 instructions a second according to
>     experts who read the design, it can to at most 3
>     instructions a second.
>

Well this was a P-4 vs Athlon, _not_ a P-3. So optmization for a P-3 would have
no bearing in this case. I find much of the data about the P-4 at this site very
suspect.
There appeared to be no serious branch misprediction, and it flew past the
Athlon chip.
>>

The Fritzmark for the Pentium was 749 and the AMD a mere 548! Why? This is
>>contrary to the findings of this forum. That is a difference of 201, that is
>>large!
>>
>>An explantion would be appreciated, thanks!
>>
>>Terry



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