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Subject: Re: Here are some actual numbers

Author: Tom Kerrigan

Date: 20:39:22 04/12/03

Go up one level in this thread


On April 12, 2003 at 22:44:09, Vincent Diepeveen wrote:

>On April 11, 2003 at 16:53:59, Tom Kerrigan wrote:
>
>>On April 11, 2003 at 10:58:29, Robert Hyatt wrote:
>>
>>>I have explained "why not" before.
>>>
>>>My configuration is a dual 2.8.  I can't remove a CPU because I don't have a
>>>terminator to
>>>stick in the socket.  So I am stuck with two.  I can enable or disable SMT when
>>>I boot the
>>>machine.
>>>
>>>now tell me how to run the test.  Two copies might run on one physical cpu
>>>(using two
>>>logical cpus).  Or they might run on two physical cpus.  I have no control over
>>>that.  And
>>>they will bounce around between processors as they run.
>>>
>>>Your turn.  Tell me how to run a valid test and I'll let 'er rip.
>>
>>Actually a friend of mine has access to a P4/3.06 and I ran the test myself.
>>Took less than 5 minutes.
>>
>>I opened two instances of my program and had them search the same position
>>simultaneously and compared their NPS after ~10 seconds. I did this three times.
>>Task Manager showed that both logical processors were pegged. The NPS ratios
>>were:
>>
>>51%-49%
>>49%-51%
>>48%-52%
>>
>>It's pretty darn obvious that HT does not favor one logical processor more than
>>another. (Contrary to Hyatt and Vincent's assertions.)
>
>I do not see why this is contrary to my assumption. What i see is that SMT
>improves nps with say 15%. How that is divided between the 2 processes i didn't
>write down anything about here.

"with SMT that is not the case. the second cpu in SMT delivers somewhere between
0% and 20%."

-Tom



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