[RC5] Prescott Performance and New Core

Slawek sgp at telsatgp.com.pl
Sat Feb 14 06:21:22 EST 2004

In message to <rc5 at lists.distributed.net> sent Fri, 13 Feb 2004
17:20:11 -0600 (CST) you wrote:

 SN> The newly announced/released Pentium 4 Prescott contains some potential
 SN> performance inprovements over previous versions of the Pentium 4
 SN> processor. Specially the shift/rotate unit has been moved from the
 SN> complex integer unit to one of the simple integer units. This means
 SN> that a rotate can be completed in half a clock cycle as opposed to the
 SN> previous 4-6 clock cycles. Since RC5 depends heavily on a rotate
 SN> instruction this improvement potentially could increase the Prescotts
 SN> speed. Of course a new core needs to be developed to take advantage of
 SN> this redesign.

I don't know yet, if Prescott can execute more than 3 uops per cycle. I
haven't had time to look at it.

If it can, than yes, it's possible to get preformance boost. If it can't,
than my Pentium 4 core does already execute 3 uops per cycle even with old
slow rotator (it working with other pipes in the mean time).

On the other hand - from what I can see at first sight - the cores should
work *MUCH* faster with Prescott's hyperthreading, even without redesign.
Does anybody have Prescott handy to check this?

Slawomir Piotrowski

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