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Subject: Re: The need to unmake move

Author: Eugene Nalimov

Date: 20:45:44 08/29/03

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On August 29, 2003 at 23:18:43, Jeremiah Penery wrote:

>On August 29, 2003 at 22:19:59, Eugene Nalimov wrote:
>
>>Sorry, from SPEC Rate I see only that *independent* processes scales well. Any
>>OS with minimal NUMA knowledge will allocate data for each processor in its
>>local memory, thus totally avoiding such problems.
>>
>>And are you sure that NUMA system that for independent processes "scales almost
>>as well" as shared-bus shared-memory system is really good achievement?
>
>I used the words "nearly as well" without checking.  In CINT Rate, Opteron (from
>what I could tell) at 1.8GHz scales at somewhere over 95% from 1 to 4
>processors.  Itanium2 scales at 97+% in IntRate.  So Opteron is marginally worse
>here.
>In CFPRate, however, the situation is much different.  Opteron scales (from
>different sets of numbers) still around 90%, while Itanium2 drops horrifically
>all the way to near 70% efficiency.

Itanium2 started from much higher initial score, so it saturated available
bandwidth earlier. SpecFP applications like lot of bandwidtdh -- trust me... I
believe hypothetical (much) higher-clocked Opteron with FP performance
approaching Itanium's will also have worse scaling.

In any case, 4-CPU SpecFP rate Itanium2 scores are still much better than
Opteron scores. And I don't see 16/32/64 Opteron scores at SPEC web site,
probably you can explain why :-) ?

Please notice: I don't have anything against Opteron/Athlon64. Very good CPUs
with solid performance. I just strongly react to all the hype...

>Remember also that this is Itanium2 with good compiler support against first
>generation Opteron without even decent AMD64 compiler (GCC is not horrible, but
>ICC 32-bit is still much faster - PGO's compiler apparently blows goats for
>compiling SPEC for AMD64, see
>http://www.digit-life.com/articles2/insidespeccpu/insidespeccpu2000-opteron2.html
>).

Till recently everybody was saying "EPIC needs compiler breakthrough that cannot
be achieved, while OOO CPUs don't need that breakthrough". And now it happens
that EPIC compiler already there...

Thanks,
Eugene

>However, compared to *every* other processor with submitted SPECRate scores,
>Opteron has better scores than every one except a couple of Itanium2 systems and
>a single Power4+ system (of systems up to 4 processors), and scales better than
>everything except those Itanium2 systems in CINTRate.



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