Prime95 underutilized?

2005-02-02, 01:20

Sorry if this is (a) really dumb; or (b) in the wrong place.

I'm running Prime95 on a P4 with hyperthreading. When I look at the processor usage, Prime95 never gets above 50% and the system idle process take up the rest. Does this really mean that Prime95 is only using half the processor, or does it just look that way because of the hyperthreading?

Thanks for any help.

marc · 2005-02-02, 02:55

Lots of people ask about this.

Check http://www.mersenneforum.org/showthread.php?t=3064 for lots of info.

The basic info is that prime95 is running at full speed and the 50% is just hyperthreading. Some people say running 2 instances of prime95 will have higher throughput overall even though each individual process is slower. Others say this is especially of benefit if you run one instance doing LL testing and another doing trial factoring. You can always run your own tests.

2005-02-02, 01:20	#1
mersennegoblue 2·293 Posts	Prime95 underutilized? Sorry if this is (a) really dumb; or (b) in the wrong place. I'm running Prime95 on a P4 with hyperthreading. When I look at the processor usage, Prime95 never gets above 50% and the system idle process take up the rest. Does this really mean that Prime95 is only using half the processor, or does it just look that way because of the hyperthreading? Thanks for any help.

2005-02-02, 02:55	#2
marc Jun 2004 UK 139 Posts	Lots of people ask about this. Check http://www.mersenneforum.org/showthread.php?t=3064 for lots of info. The basic info is that prime95 is running at full speed and the 50% is just hyperthreading. Some people say running 2 instances of prime95 will have higher throughput overall even though each individual process is slower. Others say this is especially of benefit if you run one instance doing LL testing and another doing trial factoring. You can always run your own tests.