[RC5] hyper threading on Intel P4

Adam Crews Adam.Crews at Procket.com
Thu Dec 19 22:02:42 EST 2002

It appears that the new P4 3.06 ghz chip with intel's hyper threading performs much much slower when 2 rc5 threads are started.  This chip presents it's self as 2 cpu's to the OS, and as a result dnet automatically starts 2 threads.  The client version is dnetc v2.9001-477-CTR-02111118 for Win32 (WindowsNT 5.1).
When this happens, the machine cracks a horid 2 million keys a second.
[Dec 19 05:36:48 UTC] 2 crunchers ('a' and 'b') have been started.
[Dec 19 15:25:07 UTC] RC5-72: Summary: 18 packets (18.00 stats units)
                      0.09:51:44.17 - [2,117,507 keys/s]

When the client is configured to only start 1 thread, it runs much better at 4 million keys a second:
[Dec 20 05:05:05 UTC] 1 cruncher has been started.
[Dec 20 05:17:04 UTC] RC5-72: Completed CA:4263E76E:00000000 (1.00 stats units)
                      0.00:11:59.10 - [4,214,779 keys/s]
It appears that the threads are steping on each other and generally slowing things down.
If the guys working on the x86 cores would like to test code on this chip, I am willing to give it a run and provide any feedback.
Or if anyone has any ideas on why this happens this way, I would be interested to know.

To unsubscribe, send 'unsubscribe rc5' to majordomo at lists.distributed.net
rc5-digest subscribers replace rc5 with rc5-digest

More information about the rc5 mailing list