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Load Voltage Osscilates

post #1 of 9
Thread Starter 
I'm using a Asus P8z77-v mobo and have it OCd to 4.4 ghz with offset voltage. I've noticed that the voltage will oscillate between about 1.216V to 1.192V in CPU-z. It's stable under 6+ hours of P95 so far, but the temperatures at the lower voltage are about 10C higher sometimes popping up to 78C on one of the cores.

Anyone have an idea what could cause this?

Cheers!
post #2 of 9
LLC changes your voltage under load.
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post #3 of 9
Thread Starter 
LLC is off. It change isn't from idle to load. It is during loading. 20 minute or so cycle between those voltages.
post #4 of 9
The load changes while Prime95 is running, and with no LLC your voltage is going to change as the load changes, that's normal. Try running with a little bit of LLC instead - Medium or High on that board. The VID can also change with load, and that can cause jumps with offset voltages as well. But if the temps are higher when the voltage is lower, that's probably LLC - the higher load is making the chip hotter , and also pulling the voltage down.
post #5 of 9
It's a combination of Spread spectrum and no LLC that's causing what you're experiencing.

LLC should be low/medium.

see http://www.ni.com/white-paper/4154/en
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post #6 of 9
Thread Starter 
Quote:
Originally Posted by Forceman View Post

The load changes while Prime95 is running, and with no LLC your voltage is going to change as the load changes, that's normal. Try running with a little bit of LLC instead - Medium or High on that board. The VID can also change with load, and that can cause jumps with offset voltages as well. But if the temps are higher when the voltage is lower, that's probably LLC - the higher load is making the chip hotter , and also pulling the voltage down.

This makes sense to me, but I just bumped the LLC up to high (50%) and I still get the same effect. I start up prime 95 get 1.200v at high 60s for temps. After about 10-20 minutes voltage drops down to 1.184v and I am getting high 70s for temps. Another 10-20 minutes later, it is back up to 1.200v.

I get that load should change the supplied voltage, but increase temps? I would think that temps and voltage would drop if the load were changing. Resource monitor reports that I have constant cpu and clock usage though so I dunno...
post #7 of 9
The greater load means more current flow (and lower voltage due to Vdroop) which means more power to dissipate, which means more heat. The load on the CPU (what resource monitor shows) will stay the same 100%, but the work the CPU is doing is different for different tests of Prime95. Try running IntelBurnTest and see what happens.

50% LLC might not be enough to fully compensate for the Vdroop - but as long as it is stable, what you have is fine.
post #8 of 9
Thread Starter 
Just downloaded IntelBurnTest and will give it a go. So you think a very high or extreme LLC setting would could completely compensate for this (I'm not saying i'm going to use them just curious).
post #9 of 9
It should, but I wouldn't use Extreme. It's okay to have a slight droop like you have, it's actually part of the Intel spec, so as long as it doesn't cause instability you can just leave it as-is.
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