[RC5] different DES-speeds

Remi Guyomarch rguyom at mail.dotcom.fr
Tue Jul 14 23:57:28 EDT 1998


Seth Bokelman wrote:
> 
> I wonder if DES doesn't like dual processor systems or something, because I
> have a dual PII-233 NT box here, that's getting 1.96 Mkeys, but at home on
> my single processor Pentium 233 MMX, I'm getting 2.1Mkeys. Anyone else have
> this experience? -Seth

On multiprocessors NT systems, we 'pin' each working thread on one
processor. But I heard some times ago that NT always do I/O on the first
processor. So if you have a lot of I/O on the machine, you will perhaps
see a decrease in performance on one thread. But it's better to 'pin'
each thread on one processor than to let NT flip-flap the cores on each
processor every second...

Another thing : DES use far more code and data than RC5. The MMX core
use ~11 KB of data and a bit less than 32 KB of code. Anything running
concurently will probably decrease the performance of DES by a larger
percentage than with RC5, due to cache misses.

-- 
Rémi		Don't waste your computer's time. Distribute it!
			http://www.distributed.net/
	    RC5 cores source code : http://altern.com/rguyom/


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