Can't seem to make Prime95 use fewer cores

2017-12-12, 10:22

I use the program for stress testing only.
I decided to up the turbo frequency in th BIOS for when only one or two cores are active, and wanted to do some testing, but I can't seem to get it to work. Current setting is 1 or 2 cores=4,6GHz, 3-4 cores=4,4GHz.
I changed the number of cores to two in the worker window under test menu, and in the torture test window I set the number of threads to 4 instead of usual 8 (I have Core i7).

Now when I run the test, all of my cores go up to 4,4GHz instead of two going to 4,6 and the rest being reasonably idle. I don't get it. Am I doing something wrong?

Prime95 · 2017-12-12, 20:23

Run the torture test with 2 threads

2018-01-04, 16:09

Quote:

Originally Posted by Prime95

Run the torture test with 2 threads

That would imply Prime95 doesn't take hyper threading into consideration, but that's obviously not true, so I don't understand.

edit: and even if I do that, all my cores go to 4,4GHz, so it doesn't work :(

Mark Rose · 2018-01-04, 16:46

Make sure you're running 1 worker with 2 threads.

2018-01-12, 22:41

Quote:

Originally Posted by Mark Rose

Make sure you're running 1 worker with 2 threads.

Did you even read my previous post?

VBCurtis · 2018-01-12, 23:28

1 worker two threads is a different workload than 2 workers one thread. That's what he was trying to clarify.

Prime95 uses CPU so thoroughly that turbo may not work at 4.6; FMA often has a different turbo speed, so 4.4 may be all you get.

2018-01-28, 13:05

Ok, thanks for the explanation.
I guess I will have to find a different type of stress testing software that would let me do this :(

2017-12-12, 10:22	#1
Octopuss 6342₈ Posts	Can't seem to make Prime95 use fewer cores I use the program for stress testing only. I decided to up the turbo frequency in th BIOS for when only one or two cores are active, and wanted to do some testing, but I can't seem to get it to work. Current setting is 1 or 2 cores=4,6GHz, 3-4 cores=4,4GHz. I changed the number of cores to two in the worker window under test menu, and in the torture test window I set the number of threads to 4 instead of usual 8 (I have Core i7). Now when I run the test, all of my cores go up to 4,4GHz instead of two going to 4,6 and the rest being reasonably idle. I don't get it. Am I doing something wrong?

2018-01-12, 23:28	#6
VBCurtis "Curtis" Feb 2005 Riverside, CA 1001100000100₂ Posts	1 worker two threads is a different workload than 2 workers one thread. That's what he was trying to clarify. Prime95 uses CPU so thoroughly that turbo may not work at 4.6; FMA often has a different turbo speed, so 4.4 may be all you get. Last fiddled with by VBCurtis on 2018-01-12 at 23:29

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2017-12-12, 20:23	#2
Prime95 P90 years forever! Aug 2002 Yeehaw, FL 2·3,767 Posts	Run the torture test with 2 threads

2018-01-04, 16:46	#4
Mark Rose "/X\(‘-‘)/X\" Jan 2013 2·5·293 Posts	Make sure you're running 1 worker with 2 threads.

2018-01-28, 13:05	#7
Octopuss 541₁₀ Posts	Ok, thanks for the explanation. I guess I will have to find a different type of stress testing software that would let me do this :(