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Why doesn't Prime95 stress my new cpu?

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a b à CPUs
April 8, 2011 3:31:01 PM

When I had a quad core cpu Prime95 would blast all 4 cores at 100% load.

Now that I have a i3-2100, Prime95 doesn't even make my cpu hit 50% load, no matter what torture test I run.

Why is that?

More about : prime95 stress cpu

a b à CPUs
April 8, 2011 3:36:54 PM

Leaps-from-Shadows said:
What are you using to judge "load"?


Coretemp and task manager.

I'm baffled because I want to see what the max temps are on this thing.
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a b à CPUs
April 8, 2011 3:48:38 PM

Is this a new Windows install?

Does your Windows install recognize all four cores?

Is Prime95 detecting that you have four cores and using four threads?
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a b à CPUs
April 8, 2011 3:52:40 PM

My cpu does not have 4 cores and 4 threads, it has 2 cores and 4 threads.

I don't see anywhere in Prime95 where it mentions cores or threads but it does recognize my cpu by name.

Yes Windows shows 4 graphs.

Yes I did a fresh Windows install last night.

CPU-Z and Coretemp both show 2 cores 4 threads.
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a b à CPUs
April 8, 2011 3:53:28 PM

Also, if you're interested, try using Intel Burn Test. It stresses a bit more than prime95. My CPU was at least 5 degrees C hotter when using IBT than p95.
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a b à CPUs
April 8, 2011 4:01:58 PM

Ok I set Intel Burn Test to maximum, it went to 100% on both cores for about 5 seconds and then it dropped down to about 50%, just like Prime95.

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a b à CPUs
April 8, 2011 4:12:26 PM

When it says 50% load, does it put all the load on one core, or does it distribute (like 50-50 or 75-25)?

When you start prime95 and choose the stress test mode, how many threads do you run? Since you have 4 threads, it should be 4 to utilize everything. Same goes for IBT, since its "Auto" selection for threads might be selecting a different value. Try setting it manually to "4".
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a b à CPUs
April 8, 2011 4:16:25 PM

gracefully said:
When it says 50% load, does it put all the load on one core, or does it distribute (like 50-50 or 75-25)?

When you start prime95 and choose the stress test mode, how many threads do you run? Since you have 4 threads, it should be 4 to utilize everything. Same goes for IBT, since its "Auto" selection for threads might be selecting a different value. Try setting it manually to "4".


It's distributed over both cores. Usually 55-45 or 50-30 and switches around. None go much over 50.

I don't see any setting for how many threads to run in Prime95. I select "torture test" then I have tried "small fft's", "in place large fft's", and "blend".


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a b à CPUs
April 8, 2011 4:20:43 PM

geekapproved said:
My cpu does not have 4 cores and 4 threads, it has 2 cores and 4 threads.

I don't see anywhere in Prime95 where it mentions cores or threads but it does recognize my cpu by name.

Your Windows install should show four cores, because it recognizes the HyperThreading cores as real cores. That's what I mean when I say four cores.

And Prime95 should have a setting for threads/cores (I forget which) in the Torture Test window where you choose Small, In-place large, or Blend. It should be towards the bottom of that window. That setting should be at four.

As long as you installed the newest Intel chipset drivers after installing Windows itself (and all of its updates) then about all I can think of is that some hidden setting in the H61 board is preventing it from fully loading all four cores. Have you checked to see whether you have the latest BIOS update?

Edit: What version of Prime95 are you running?
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a b à CPUs
April 8, 2011 4:23:54 PM

In the "Run a Torture Test" Dialog of p95, there is an option below which is labeled "Number of torture test threads to run: ".
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a b à CPUs
April 8, 2011 4:24:35 PM

Leaps-from-Shadows said:
Your Windows install should show four cores, because it recognizes the HyperThreading cores as real cores. That's what I mean when I say four cores.

And Prime95 should have a setting for threads/cores (I forget which) in the Torture Test window where you choose Small, In-place large, or Blend. It should be towards the bottom of that window. That setting should be at four.

As long as you installed the newest Intel chipset drivers after installing Windows itself (and all of its updates) then about all I can think of is that some hidden setting in the H61 board is preventing it from fully loading all four cores. Have you checked to see whether you have the latest BIOS update?

Edit: What version of Prime95 are you running?


Ok first of all, I already said Windows shows 4 graphs.

There is no setting in prime95 for cores/threads.

I installed the chipset drivers first thing as soon as I had Windows installed.

I also said that the burn test ran both cores at 100% for the first 5 seconds of the test.

Version is 24.14.

Any other theories?
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a b à CPUs
April 8, 2011 4:30:24 PM

I fail to see how a bios update will do anything. This is a fresh B3 revision board and it was made for these cpu's and it's recognized by the model number in bios. It's not as if it's an older board and I have a newer cpu.

Every other program shows 2 cores 4 threads and everything is recognized correctly.

This is pissing me the $@@% off.
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a b à CPUs
April 8, 2011 4:30:37 PM

Yes. Try the newest version of Prime95: 26.5
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a b à CPUs
April 8, 2011 4:33:48 PM

geekapproved said:
I fail to see how a bios update will do anything. This is a fresh B3 revision board and it was made for these cpu's and it's recognized by the model number in bios. It's not as if it's an older board and I have a newer cpu.

Every other program shows 2 cores 4 threads and everything is recognized correctly.

This is pissing me the $@@% off.

lol

Sometimes there are bugs in newly-released board BIOSes. Updating to the newest one, even if for whatever reason you really want to avoid it, is sometimes the only way to fix things.
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a b à CPUs
April 8, 2011 5:10:45 PM

Yes I want to avoid it, it's a brand new B3 board.

I opened about 25 pages of Google Chrome as fast as I could and the cpu had no problem hitting 100% load on both cores.

So this is not a bios bug.

I guess I'll start a new thread tomorrow to see if anyone else has any ideas why I cant hit 100% load with Intel Burn Test or Prime95.
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a b à CPUs
April 8, 2011 5:21:51 PM

Ok I got it now guys, with Intel Burn test.

I had to manually choose 4 threads from the drop down menu instead of leaving it on auto. It's running all 4 threads at 100% right now as I type this.

Thanks for the help fellas.

**It's hitting 59c with stock fan and TX-2. Surprising, but if you saw the fan that comes with this thing you would laugh. It's like the fan you used to get with a Intel 200mmx. lol
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Anonymous
a b à CPUs
April 8, 2011 5:24:08 PM

This may actually have something to do with power saving features, you should try running a multi-threaded app other than a stress test like a good video converter, you could get a trial of Sony Vegas from Sony.com and just put in some random sample videos and render them with Xvid or DivX, Xilisoft Video Converter uses all your CPU cores and allows you to enable and disable them, so in conclusion you should check if using the CPU normally would stress your CPU, rather than stress tests, some times there are a lot of problems with power saving features like one I had with my GT 240 which ran at 100MHz in non DirectX games or when I was watching and HD movie, it would lag, I disabled power saving so that it always ran at it's max clocks and it solved the problems, you can't do this with an Intel processor as this feature in Intel processors, Speed Step, is hardware, not driver based but anyways I hope this info helps.
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April 8, 2011 5:36:12 PM

59C on the stock cooler? Thats really good. I'm hitting 73C on my 2600k with a Hyper 212+ on IBT set to 8 threads. Of course I'm running a 4600MHz OC....
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a b à CPUs
April 8, 2011 5:45:23 PM

Yeah I had a Q6600 at 3200 with Core Contact Freezer and it maxed at 59c too. I expected this to be much cooler, but with this joke of a fan, I guess it's ok.

The fan is so tiny, and they don't even use copper contact anymore, it's just plain aluminum and the whole hsf is about 1.5 inches tall. Sad really. I've got an old Arctic Cooler Freezer 7 pro I'm considering digging out of the closet.
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Anonymous
a b à CPUs
April 10, 2011 2:08:54 PM

geekapproved said:
Yeah I had a Q6600 at 3200 with Core Contact Freezer and it maxed at 59c too. I expected this to be much cooler, but with this joke of a fan, I guess it's ok.

The fan is so tiny, and they don't even use copper contact anymore, it's just plain aluminum and the whole hsf is about 1.5 inches tall. Sad really. I've got an old Arctic Cooler Freezer 7 pro I'm considering digging out of the closet.



did you read my post and try it?
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August 21, 2013 1:11:57 AM

Going to bump this as it's high in Google ranking. Some of these suggestions by these "cpu authorities" are...wow.

Prime95 (v27.9 build 1) apparently isn't smart enough to utilize enough workers by default for all your available threads. I have a quad-core i7-920 with HT enabled and it defaulted to 4 workers. Not an issue though, just select 8 worker windows (in my case) and primenet will take care of the rest. If the program is already running for you at 50%, go into Test->Worker Windows...->manually set the number of worker windows to 8 (in my case)->Test->Stop->Test->Continue. Primenet will then fetch more work for the additional 4 workers (if you've selected this route in the program) and now your cpu is 100% utilized.

Right now I'm testing out a new Corsair H60 installation with an intake configuration. I'm actually worried about the dust intake on the rear so I've recently ordered a Silverstone add-on filter for that purpose. I've been at 100% utilization for about half an hour now and am sitting at a fair 63C (stock clock.) Idle temps hover just above 45C. My room is 20C ambient.
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