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Subject: Re: OT: P4- 3 GHz with hyper-threading

Author: Robert Hyatt

Date: 07:41:25 11/01/02

Go up one level in this thread


On October 31, 2002 at 10:53:07, Vincent Diepeveen wrote:

>On October 30, 2002 at 06:59:21, Terje Vagle wrote:
>
>>Hi all,
>>
>>The new cpu from intel will have a new function called
>>hyper-threading.
>>
>>This will make the operating system able to recognize the cpu as if it was
>>2 cpu's.
>>
>>Could the programs with smp-support make use of this?
>>
>>Regards,
>>
>>Terje Vagle
>
>No chessprograms cannot make use of that feature at all. It is sad but
>the truth. Hyperthreading is a cool thing for the future but the P4
>processor is a too small processor to allow hyperthreading from getting
>to work.
>
>Apart from that a major problem is that even if we have a great processor
>which really allows hyperthreading to be effective, that the threads
>run at unequal speeds.
>
>Hyper threading is supposed to work for 2 threads where 1 is a fast
>thread and the other is some kind of background thread eating little cpu
>time.
>
>In chessprograms having a second search thread which just runs now and
>then in the background is simply impossible to use.


It is not impossible at all.  The only problem was spinlocks and Eugene
posted a link to an Intel document that describes how to solve this problem.

Given that solution, hyper-threading will work just fine since spinlocks
won't confuse the processor...

It won't be 2x faster, but it will certainly be faster if you can run a second
thread while the first is blocked on a memory access...



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