Prime95 throttle?

[SkiDragon]

Is there a way to make Prime95 use less than 100% of my CPU? My system seems to run stable, but my CPU (an i7) runs very hot, around 80 degrees C. I don't think this is good for it in the long term, but I don't want to quit the exponents I am working on.

[Mini-Geek]

Of course it'd be better to upgrade your cooling and/or make sure all fans are free of dust and able to easily blow, but here's the option you were looking for:

If you are running on a laptop or in a hot room and you want to slow the
program down to reduce heat, then you can add this line to prime.txt:
    Throttle=n
where n is the percentage of time the program should run.  For example,
Throttle=40 means the program will run 40% and be idle 60% of the time.

Also, this might interest you:
http://www.pugetsystems.com/blog/200...-temperatures/
They say that i7s won't throttle until 100 C, and say:

Our recommendation is to keep Intel Core i7 CPUs under 80C. That gives you a healthy margin in case you’re running a heavy load on your CPU on a particularly hot summer day. Due to the manufacturing process of Intel Core i7, and the improved power management features, we’re comfortable at up to 80C, even though this would be considered a very hot temperature with an Intel Core 2 Quad CPU.

(note this is on the site of a company that makes a cooler, so I wouldn't say it's a totally unbiased source)

[SkiDragon]

That option works, but it's not really what I need. I set it to 50 % and by monitoring the task manager it looks like the calculations start and stop every couple of seconds. This would be fine, but for some reason a fan inside my computer turns on whenever the calculation starts, and turns off when it is done, which means the fan turns on and off every couple of seconds, which is very annoying.

Is there some way to just have it run at 50 % CPU continuously, instead of 100 % on and off?

[Mini-Geek]

Well, you could just run workers for half of the cores. I think this would produce the results you're looking for, i.e. steady fan motion and lower temperatures.
It'd probably be best to set one worker on core 1 and the other on core 4, to keep them as far apart (physically, for heat, and also to be more sure to have memory bandwidth available) as possible. In any case, you'd definitely want them on separate physical cores.
You can use the AffinityScramble option to make it set the affinities how you want.

You can arbitrarily change how the program assigns affinity to CPUs.
The program makes its best guess at assigning workers and helper threads
to CPUs for optimal speed.  However, new architectures or situations we
haven't considered may make different affinity setting desirable.  In
local.txt set
    AffinityScramble=string
Where the string "0123456789ABCDEFGHIJKLMNOPQRSTUV" is the "make no
changes" string.  For example, let's say you have a system with 8 logical
cores with 4 workers each using a helper thread.  The program would
ordinarily assign the worker and helper threads to [0,1], [2,3], [4,5], [6,7].
However, if you think [0,2], [1,3], [4,6], [5,7] would give better performance,
you would set AffinityScramble=02134657 to test out your theory.

I think AffinityScramble=06 would be what you'd want. (if running two single-threaded workers)

[joblack]

Originally Posted by SkiDragon

That option works, but it's not really what I need. I set it to 50 % and by monitoring the task manager it looks like the calculations start and stop every couple of seconds. This would be fine, but for some reason a fan inside my computer turns on whenever the calculation starts, and turns off when it is done, which means the fan turns on and off every couple of seconds, which is very annoying.

Is there some way to just have it run at 50 % CPU continuously, instead of 100 % on and off?

Even with a temperature of 80 C it's not a problem. I have running my Core2Duo Q6600 with around 80 C for more than a year.

In my 'computer freak career' I never had a CPU burned through. At most the computer would freeze.

I suggest to get another cooler and it will be fine. Don't worry so much about it.

Anyway even if you only use 50% performance you will get the same problem with a game or program which uses the complete performance.

PS: You can turn your cooler permanently in the BIOS ...

[retina]

Originally Posted by joblack

PS: You can turn your cooler permanently in the BIOS ...

I think you a word out.

[Mini-Geek]

Originally Posted by retina

I think you a word out.

Me too, but you could interpret 'turn' as referring to turning the fan around, not turning the fan on, and then it's closer to ok.
"PS: You can turn your cooler around permanently in the BIOS ..."

[joblack]

Originally Posted by Mini-Geek

Me too, but you could interpret 'turn' as referring to turning the fan around, not turning the fan on, and then it's closer to ok.
"PS: You can turn your cooler around permanently in the BIOS ..."

It's great how a missing word is amusing to all the little forum kids ;).

"You can permanently turn on your cooler in the BIOS options ..."

[Dougal]

It's great how a missing word is amusing to all the little forum kids ;).

"You can permanently turn on your cooler in the BIOS options ..."

yes,and it's almost a sin to one person.

[SkiDragon]

Originally Posted by Mini-Geek

Well, you could just run workers for half of the cores. I think this would produce the results you're looking for, i.e. steady fan motion and lower temperatures.
It'd probably be best to set one worker on core 1 and the other on core 4, to keep them as far apart (physically, for heat, and also to be more sure to have memory bandwidth available) as possible. In any case, you'd definitely want them on separate physical cores.
You can use the AffinityScramble option to make it set the affinities how you want.

You can arbitrarily change how the program assigns affinity to CPUs.
The program makes its best guess at assigning workers and helper threads
to CPUs for optimal speed.  However, new architectures or situations we
haven't considered may make different affinity setting desirable.  In
local.txt set
    AffinityScramble=string
Where the string "0123456789ABCDEFGHIJKLMNOPQRSTUV" is the "make no
changes" string.  For example, let's say you have a system with 8 logical
cores with 4 workers each using a helper thread.  The program would
ordinarily assign the worker and helper threads to [0,1], [2,3], [4,5], [6,7].
However, if you think [0,2], [1,3], [4,6], [5,7] would give better performance,
you would set AffinityScramble=02134657 to test out your theory.

I think AffinityScramble=06 would be what you'd want. (if running two single-threaded workers)

I tried "AffinityScramble=06", but it doesn't seem to affect anything. The CPU still seems to run at 100%, and at 80 degrees C, and the fan still runs all the time.

Is there a way for people to take over the exponent that I have half tested, and finish testing it? That would be a good feature.

[Mini-Geek]

Originally Posted by SkiDragon

I tried "AffinityScramble=06", but it doesn't seem to affect anything. The CPU still seems to run at 100%, and at 80 degrees C, and the fan still runs all the time.

Did you set the number of worker windows (in Test > Worker Windows) to 2 and the number of threads/cores for each to use to 1 first? I find that highly unlikely, since two single-threaded threads can't use more than about 50% of an i7. You need to do that like I said in addition to the AffinityScramble.
You'll want to make sure the assignments you've got partly done on the other workers will finish, so open the worktodo.txt file and merge them over. e.g. if your worktodo.txt looks something like:

[Worker #1]
Test=ABC...

[Worker #2]
Test=DEF...

[Worker #3]
Test=GHI...

[Worker #4]
Test=JKL...

make the change in Prime95 to make it 2 worker windows, then close Prime95, and edit worktodo.txt to look like:

[Worker #1]
Test=ABC...
Test=GHI...
 
[Worker #2]
Test=DEF...
Test=JKL...

then start Prime95 again.

Originally Posted by SkiDragon

Is there a way for people to take over the exponent that I have half tested, and finish testing it? That would be a good feature.

Technically yes, since anybody could use the save files you're generating along the way, but there is no automated way built-in to PrimeNet to transfer them, mainly because moving around multi-MB files (especially on a system/program that's normally purely small text-only comms) is problematic. It'd be better to finish it yourself on another core/worker or another computer. Or, if you really don't want to finish it yourself, but really do want your work so far to help, you could upload the save files somewhere and post on this forum, requesting someone else take them over. You'd want to PM the new owner the assignment keys so that PrimeNet will acknowledge the transfer properly.