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2500k - One CPU core slower than the rest in Prime 95 with higher overclock?

post #1 of 16
Thread Starter 
I've been toying around with bumping my overclock back up to 4.7GHz (been running at 4.4 for temperature reasons, but I based that mostly on Intel Burn Test, which gets things WAY hotter than any normal program does) I loaded my 4.7GHz preset in with AI Suite II (software based, I haven't tried setting it in the BIOS yet, I do most of my stability testing within Windows first, then reproduce my settings in the BIOS once I've got a pretty good idea of what's stable)... and started Prime 95 on the Blend setting to see how hot it was gonna get, and if it was still stable. Rather quickly I noticed Worker #1 (running on logical core #0) was falling behind the rest of the workers in terms of how many tests it was getting through. After 15 minutes of testing.... Worker 1 completed 11 tests, while the other three completed 18 tests. There were no errors/crashes, but that doesn't seem right...

I was using the computer while the test was running, browsing some forums and listening to music. I didn't think that should affect it that much, but I shut everything down and ran the test again... with similar results. So I bumped it back down to the 4.4GHz setting I have been using and ran the test again. This time it's closer. Worker 1 completed 14 tests, worker 2 completed 16 tests, and workers 3 and 4 completed 17 tests in 14 minutes of testing at 4.4GHz. Similar usage to the first time I tested, listening to music and browsing forums.

Because I wondered if it was an issue of not enough voltage, I set the voltage to the same level I usually run at 4.7GHz (~1.328V under load) but with a multiplier of 46 instead. I didn't want to bump the voltage up much higher for 4.7GHz just yet as temperatures were already approaching my safety limit (they maxed out at 73C, and I want to keep it below 75C) I was watching some of the E3 coverage on G4, so this time the test ran for longer... but after 21 minutes, Worker 1 completed 24 tests, worker 2 completed 26 tests, and workers 3 and 4 completed 27 tests. (which if you do the math for tests completed per minute... 4.6GHz is technically faster than 4.7GHz... in Prime95 at least)

So, what's going on here? Is Core 0 having issues, or is it a voltage thing? 4.4 and 4.6GHz seem okay, but the difference when I tried 4.7GHz is kind of alarming, especially considering I was running at that frequency for about 2 and half months before.
Edited by Adappy - 6/7/11 at 11:52am
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My first build
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post #2 of 16
Can you make a tl;dr version please ?
post #3 of 16
Quote:
Originally Posted by Abs.exe;13786781 
Can you make a tl;dr version please ?

Honestly? You couldn't take the 30 seconds to even skim that? ~ And we wonder why the world is failing.

One of the interns in my office has a 2600k, OC'd to about 4.6 and it does the same thing...In some apps the core is tested, in others it basically sits idle.

As long as you're not getting any errors, I honestly wouldn't worry about it.

In my opinion, it seems to be a flaw in Prime95's testing of cores on the P67 platform.
post #4 of 16
Thread Starter 
Quote:
Originally Posted by Abs.exe;13786781 
Can you make a tl;dr version please ?

My CPU runs slower overall at 4.7GHz than it does at 4.6GHz with the same voltage, because of one core running much slower than the other three wink.gif
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post #5 of 16
Quote:
Originally Posted by Abs.exe;13786781 
Can you make a tl;dr version please ?

You want him to make a "Too long/Didn't Read" version of this?

It's long enough as it is. Why would u want one 'that's too long that you didn't read it' for?
    
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post #6 of 16
I had similar issues with my 2500k. I just test with IBT instead.
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post #7 of 16
Enable Round-off checking
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post #8 of 16
nevermind
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post #9 of 16
Most likely a voltage thing. Try increasing the speed in smaller increments up from 4.6Ghz instead of jumping straight to 4.7Ghz.

Have you tried IBT? If it´s fine @ 4.7Ghz in IBT you´re probably not going to run into any problems, even though it fails Prime95.
Edited by Goaky - 6/7/11 at 12:14pm
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post #10 of 16
Thread Starter 
It runs hotter than I'd like in IBT, but it passes. I wouldn't say it's "failing" Prime 95 either, just acting weird. I'll mess with it after I get home from work tonight.
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My first build
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Intel i5 2500k @4.7GHz ASUS P8P67 Pro EVGA GTX 580 (890/2075) 2x4GB G.Skill RipjawsX DDR3 1333MHz 
Hard DriveOSMonitorKeyboard
500GB Caviar Black + Spinpoint F3 1TB Windows 7 Professional x64 ASUS VH236H 23" Logitech G110 
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