Intel e6600 Dual Core Problem - How to use both cores with Prime95?

Good Day.

I'm trying to use Prime95 to stress test my new processor (not overclocked). Last night it appeared that I had both cores working (100% utilization under performance tab in windows task manager). Today I can only get 50%? I tried setting one core to 0 and the other to 1 in the affinity setting. No luck. I copied Prime95 to another folder and ran it as the second instance. Still only 50%? Any advise for a newbie? Thanks.

[Prime95]

Originally Posted by Shoallakeboy

Any advise for a newbie? Thanks.

Are both torture tests set to run in-place FFTs (not blend)

[S485122]

You could take a look at the MersenneWiki: Torture Test where a new paragraph explains your problem.

Torture test on a multicore or multiprocessor computer

If you have two instances of prime95 running torture tests on a dual core using the default "Blend" setting, the first instance each will use about 3/4 of memory the system memory. The second instance will try to do the same. The end result is that only the first instance will show some progress.

To effectively stress all cores, one must use the "Custom" setting and adapt the amount of memory to share the available amount between theall the instances of Prime95.

For example suppose a system with a dualcore processor and 2GB of memory running Windows XP needing about 256MB of memory. There is 1782MB of free memory. The sum of the "Memory to use" parameters should not exceed 1792MB. One could use 891MB (half of 1782MB) in each instance of Prime95.

The explanation of undocumented features given in undoc.txt and the "Advanced Features" of the help file is no longer applicable to the current version of the program. In other words the "TortureMem=n" line in prime.ini is not taken into account.