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Old 2007-03-29, 14:58   #1

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Default Any way to reduce CPU usage?

I'm running a dual core 2.4Ghz 2gb RAM dimension 9200, windows XP. Currently I'm running prime95 on one core, unassigned. My dad, however, is not terribly happy about having one core at 100% all the time. Is there any way to limit the amount of CPU prime95 uses? (for some reason he'd much prefer 50% usage on both cores by prime95). He's worried that it may damage the hardware in some way, before it becomes redundant.

Also, is there any difference between what system idle process and prime95 do? It's because CPU usage shows up as 50% all the time he's worried, so if I can tell him "actually, prime95 and system idle process basically do the same thing, but system idle isn't displayed" then he should be ok about having it run.
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Old 2007-03-29, 16:09   #2
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Mini-Geek's Avatar
"Tim Sorbera"
Aug 2006
San Antonio, TX USA

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Originally Posted by Jarl View Post
so if I can tell him "actually, prime95 and system idle process basically do the same thing, but system idle isn't displayed" then he should be ok about having it run.
I doubt System Idle Process searches for Mersenne primes, so I think he'd be right on that account.
Getting on to slightly more useful topics...
Here's a brief summary of what it says about what the idle process actually runs:
Originally Posted by Wikipedia
The process runs in the background and constantly monitors processing bandwidth, occupied memory and the Windows virtual paging file.
I don't know of a way to make it only use 50%, but I do know that if you have it running on two cores, they'll need to each have their own Prime95 process, unless you want to use the new version that is multi-threaded so it runs on multiple cores/CPUs (but that lowers the efficiency, so you might want to just have them run two processes).
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Old 2007-03-29, 20:31   #3
dsouza123's Avatar
Sep 2002

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Adding the throttle option to prime.ini will reduce the CPU usage.

From the Prime95.chm (compiled help file):

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.ini:


where n is the number of milliseconds to sleep after each iteration.

So add


to the end of the prime.ini file.
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Old 2007-03-29, 21:03   #4
rx7350's Avatar
Feb 2006

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The two main factors that will have a tendency to reduce cpu life are the amount of cpu voltage over stock, which can be increased as a result of overclocking, commonly referred to as vCore, and the thermal level of the cpu, on a sustained basis. Since your machine is a Dell, it's highly unlikey you have overclocking options in your BIOS, and it's probably running at the stock vCore. Running cpus at 100% load does increase the cpu temps, but as long as your cooling solution (heat-sink-fan, etc) is robust enough to keep the cpu temps below certain levels, there should be a minimal decrease in cpu life. If your pc has a Core2 Duo cpu in it, download the Intel Thermal Analysis Tool (TaT) from, or SpeedFan if it's a Pentium D, and check the cpu temps under full load - both cores running a Prime95 instance. A VERY safe cpu temp under 100% is 55C. The maximum thermal limit on CORE2 Duos cpus is 85C, at which point the cpu will certainly be 'throttling' to protect itself.

Modern day cpus will last, on the average, 12-15 years. The odds of a cpu failing because of a constant 100% load is very small, even with low to moderate (1-20%) overclocking. In your case, your sytem is running at stock, so the risk is even less so. Your pc will probably become obsolete well before it fails.

What running your system at 100% constantly WILL DO is use a little more electricity, and heat up the ambient air around the machine.

I run PRIME95 on six dual-core, Pentium Ds and Core2 Duos, 24x7, and I'm not at all concerned that doing so will result in pre-mature failure.

IMHO, as long as your Dell doesn't get too 'hot', there's very little risk (i.e., nil) of failure due to running two instances of PRIME95 at 100% load on both cores.
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Old 2007-03-29, 21:52   #5

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Ok, thankyou very much rx7350. I'm currently running two seperate torture tests (the maximum energy+heat one on each core) and neither is going above 40 C, so all seems ok. The strange thing is I can't get solid 100% CPU usage for some reason; it fluctuates around 90%, but when I ran two without copies of prime95 a while ago (not stress testing) it was at solid 100%.
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Old 2007-03-30, 19:13   #6

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Ok, i'm getting solid 100% usage again, but for some reason my dad's decided that running the computer at 100% usage, at 40 C will damage it irreparably before it becomes redundant (lol...), so i've been banned from using prime95.

twat ¬¬
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