Vcore is lower during load vs Idle

[faustfict]

Using a 2500K w/ Gigabyte UD3H-B3 Z68. 2500K is revision B2 if that helps any, also the chip is overclocked to 4.5ghz @ 1.35(Anything else the system is unstable), temperature is around 29c idle and 59 @ load. Everything is set to auto minus the 45 multiplier and Vcore, Turbo is disabled.

So when I an idle the cpu drops to 1.6ghz w/ a vcore of 1.35-136, when I'm running a stress on it with IntelBurnTest/P95, the Vcore is around 1.29. So whats the deal with this, why is the Vcore much lower when it's at 100% load vs doing nothing. Is it my settings? PLL, is all auto. Any suggestions or information requests will be welcomed.


Thanks,

 

[nna2]

when cpu load line calibration is disabled, the cpu will "thermo throttle" meaning the hotter it gets, the less volts it puts in

 

[alexandergc]

i read something about this in another forum...it has to do with power draw and silicon conductivity being related to temperature.

as the silicon heats up, it becomes a better conductor, ergo: less resistance.
so the processor puts in less voltage for the same power output due to the Ohm's Law relationship of V= IR. to maintain current, as resistance drops, voltage drops.

 

[k1114]

Sorry to debunk nna2 and alex but this is called vdroop.

 

[alexandergc]

Sorry to debunk nna2 and alex but this is called vdroop.

but does it work something like what i posted? i can't remember the details, that's just my understanding of the info i read about voltage droop.

 

[k1114]

No vdroop is for safety, when load changes, voltage will waiver before stabilizing. To keep the spikes under safe voltage, vdroop is introduced.
With vrdoop: http://images.anandtech.com/reviews/cpu/intel/penryn-oc2/transient_vdroop.jpg
Without vdroop: http://images.anandtech.com/reviews/cpu/intel/penryn-oc2/transient_no_vdroop.jpg
(Big pics so I'm just posting the links)
These are old pics showing a fixed voltage like the op is using but if uses he offset vcore, speedstep and c1e will kick in so he can have lower volt in idle and higher in load. And then he will not have to mess with adjusting vdroop and worrying about the spikes. What you said does happen but it's a much smaller amount that the vrm will handle and supply a steady voltage.