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CPU slows down when running Prime 95

Last response: in Overclocking
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August 29, 2010 1:27:03 AM

Setup:

Athlon II X3 440 @3.0Ghz - Currently OC'd to 3.6 Ghz
ASUS M4A88T-I Deluxe (http://www.newegg.com/Product/Product.aspx?Item=N82E168...)
4 GB Kingston Hyper-X DDR3 1333 (running at 1290 or so)
Seagate 7200 RPM HDD
Using Radeon 4250 IGP at the moment
Windows 7 Home Premium

CPU voltage is at 1.48. The overclock appears stable.

The problem is that when I run Prime 95, every 8-10 seconds the voltage drops to 1.1v and the CPU multiplier goes from x15 to x4. It hangs like that for about three seconds then goes back to full speed.

- Strangely, when I'm not running Prime95 the CPU stays at full speed.
- Heat is about 46 idle, 63 under full load
- HT is 2400, but when I drop it down some nothing changes.
- I have Cool n' Quiet turned off in the BIOS.

I'm fairly new to overclocking so maybe I'm missing something obvious. But I searched the forums for help and didn't find anything helpful. Thanks in advance for any input you vets might have. :) 
a b K Overclocking
a b à CPUs
August 29, 2010 1:53:28 AM

Sounds like the built-in thermal-protection is throttling your CPU, 63C is above the limit for most AMD processors.
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August 29, 2010 2:59:52 AM

At times it will hit 64-ish. I'll investigate and then check back in a bit. Is there any way to disable this kind of thing?

Also, since the CPU throttles down when running Prime 95 is the overclock really getting tested? After all, it's not staying at full load...
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a b K Overclocking
a b à CPUs
August 29, 2010 4:06:42 AM

Even if you could disable it, I don't think you want to. Silicone doesn't smell very good when it's burning.....
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August 29, 2010 4:18:26 AM

So... would you consider the overclock to be stable? Since it passes Prime 8+ hours, even though it throttles down like this? Would you recommend that I roll the speed back a bit?
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a b K Overclocking
a b à CPUs
August 29, 2010 5:20:54 AM

I think you will be OK as is. But you may want to game with it for an hour or 2 (or what ever the most intense program you normally use) while monitoring your temps. Personally I would try to stay below 60C on the CPU.
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a b À AMD
a b K Overclocking
a c 103 à CPUs
August 29, 2010 7:21:12 AM

The voltage looks high for the overclock try it lower it should lower the temps. What cooler are you using?
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September 5, 2010 4:02:44 AM

Just the stock cooler. On a M-ITX board my options are few.

I reverted the voltage to the default value and scaled back the OC to 3.46 ghz. It's giving me temps that max out at 61 under Prime and stability.
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a b K Overclocking
September 8, 2010 11:34:50 AM

unclefester said:
I think you will be OK as is. But you may want to game with it for an hour or 2 (or what ever the most intense program you normally use) while monitoring your temps. Personally I would try to stay below 60C on the CPU.


One thing to realize is that I doubt you'll find a game that will push your CPU as hard as Prime95 does. Prime95 will use all your cores to the max, which is more than any game will do that is out on the market, so if your CPU is passing Prime95 without any issues (I don't go 8 hours. If within 30 minutes you don't crash, that's usually a good sign, but others have differing opinions on that), then it's safe to bet you'll be fine with games and you shouldn't see them stress the CPU as much as Prime95 does.

Just remember that a lot of games can be more GPU intensive at times than CPU. It just depends on what and how the developers programmed the game.

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