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Subject: Re: Multiple processors on one chip...

Author: Tom Kerrigan

Date: 17:56:05 03/05/00

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On March 05, 2000 at 10:19:59, Robert Hyatt wrote:

>>I don't see why you want to bring the cache into this, if you just want to
>>compare the cores. (Which I do.)
>two reasons.  (1) if a program fits totally in cache, you are testing one
>aspect of the cpu.  If the program doesn't fit into cache, you add memory
>bandwidth and cache miss handling into the equation.  (2) "core" speed is
>only important for a program that fits completely in cache.  I am not aware

This is straying from my original question. I'm not trying to prove that the P5
is better than the P6, because it isn't. I just want to know what kind of
concrete performance improvement we are getting from these nifty new
microprocessor features.

>>>Which means no register jams occur in the program.  For more complex programs,
>>>the renaming logic in the P6 avoids many register jams/spills and does much
>>>better keeping both pipes filled.
>>Do you have any proof of this?
>This is a trivial thing to consider.  If you have 1 register, try to figure
>out a way to keep 2 instruction pipes busy, since both can't update that one
>register in one cycle, nor can one update while the other reads.  If you have

Yes, I know exactly how all of this stuff works. I'm still only interested in
the concrete improvement (and not necessarily for the x86). I thought I made
this extremely clear a few posts ago. If you don't have any actual data, I'm a
little confused as to why you're replying to my posts.

-Tom



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