Prime95 With two CPU's

MrBean · Jun 7, 2003

I Have a P4 2.6C with hyperthreading, and im trying to run one instance of prime95 on each of the cpu's. However when i try to start a new p95 it wont launch for the second time, if anyone knows how to fix this it would be awesome.
Thanks

dustybyrd · Jun 7, 2003

you need to make another folder for prime95....call it prime95-2 or something...then copy all the prime95 files to that folder and rename the exe file to prime95-2 then run that program and the original prime95 exe file...

glock19owner · Jun 7, 2003

Don't know if this helps are not...found it on Prime95's site

***************************
Dual CPU machine instructions
***************************

Detailed instructions for one way to run duallies (for those that want them):

1. Install the regular client.
2. Now, from the 17OB home page, click on the SMP client link and copy it to the same folder that the original client was installed to.
3. Run the regular client (configure it, start it).
4. To start the SMP client, I just went to the folder and dbl clicked on the executable. You'll have 2 windows, both will be labled "17 SB vx.x.x" (the version number)

Vatt · Jun 7, 2003

No need for new folder if you are only stress testing.

Just add -a1 to the second shortcut

So it reads like this:

"C:\Program Files\Prime95\Prime95.exe" -a1

MrBean · Jun 7, 2003

Thanks for your help i got the two instances running, but after a minnute or two of 100% load on both processors it drops down to almost nothing and wont come back, does anyone know what is causing this? When i set it to run on any cpu it stays at 50% and the page file history looks strange it goes up and then down to nothing on about one inch intervals. What are you guys doing to stress test your ht processors cause i cant seem to get this to work right.

ozziegn · Jun 7, 2003

you're having some sort of hardware failure.

it could be anything from your RAM not being able to be worked that hard or your chip might be getting too hot, maybe not getting enough voltage or just being O/Ced too high if in fact it is.

just depends.

I'd back off a little if you're O/Cing and see what it does then.

MrBean · Jun 7, 2003

This was a 2.6c not overclocked with somewhat relaxed ram settings, i cant figure it out, what version of prime 95 are you guys running. And also if you only run one instance is it only possible for it to get to 50% cpu usage?

ozziegn · Jun 7, 2003

MrBean said:
And also if you only run one instance is it only possible for it to get to 50% cpu usage?

yes, providing that you have HT enabled in the BIOS, your CPU will only run at 50% usage with running only one instance of Prime 95.

MrBean · Jun 7, 2003

yes I have ht enabled. Is this truly only using half the processor, or is it just windows reading it wrong. Is anyone out there able to keep it under 100% load, using two instances because mine just doesnt seem to work.

NookieN · Jun 8, 2003

Windows reporting 50% CPU usage while running Prime95 is not accurate. Prime is using almost all of the CPU resources that it can with just one instance (especially if you're using v23.4). I and several others have verified this by experiment (there are a few threads on the topic at mersenneforum.org).

Running two instances of Prime with HT will probably not stress your chip more that one instance. Feel free to do it if you're bored or anal though.

Vatt · Jun 8, 2003

Best thing is to set the memory usage per instance to half your RAM.

If you have 512 MB of RAM, set instance 1 to use only 200 MB and instance 2 also 200 MB.

Under preference or CPU you can change that. That way it will work without problems. Otherwise it spends more time swapping than calculating (exactly what you are seeing)

zabomb4163 · Jun 8, 2003

MrBean said:
I Have a P4 2.6C with hyperthreading, and im trying to run one instance of prime95 on each of the cpu's. However when i try to start a new p95 it wont launch for the second time, if anyone knows how to fix this it would be awesome.
Thanks

eh? each of the CPUs? maybe i'm just stupid but what exactly would be the benefit of running 2 instances of prime instead of one besides creating more overhead? hyperthreading just ACTS like two processors. unless you meant you had xeons and accidently said p4, otherwise it sounds sort of silly to me.

ozziegn · Jun 8, 2003

NookieN said:
Running two instances of Prime with HT will probably not stress your chip more that one instance. Feel free to do it if you're bored or anal though.

oh really?

so why is it that when I run two instances of Prime 95 using the affinity to CPU "0" and "1" that my processor temps are on the average of 4C higher than by just running one instance of Prime 95?

care to enlighten me or am I just being anal?

zabomb4163 · Jun 8, 2003

i get highest temps runing folding@home and prime at the same time.

TheGr8s1 · Jun 8, 2003

i can never get 100% cpu usage even if I ran 3 prime95's. LOL Cpuidle shows it around 50%/75%. I suppose I need to turn off cpu idle?

Vatt · Jun 8, 2003

My findings with running 2 instances of Prime95 instead of 1:

-temps increase by 5*C ( -3*C rising to +1*C )
-failing at speeds where 1 instance would show no errors
-CPU usage at 100% instead of 50% when using 1 instance

I only use Prime for torture test.

I have made 2 shortcuts on the desktop.
1 shortcut is normal, the other one has the -a1 switch added to it.
I have 1024 MB of RAM and set each instance to use a maximum of 400 MB, otherwise it spends more time swapping than calculating.

This way is the best torture test available.

However, Sandra CPU arithmatic would not run, even with 2 Prime's running stable! So a combination of programs is still needed to get perfect stability.

steliosDj · Jun 8, 2003

Agree ! .. running two prime95 with affinity stresses the CPU a lot !!
I can also check it on my multimeter where the voltage drops about 0.1-02 Volts ....
Also the taskbar shows 100% usage all the time with no drops !

Prime95 With two CPU's

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