Voltage fluctuation!

xxShinobixx · 7 Feb 2012 at 17:30

Hi all,
I started playing around with my CPU and decided to go for a little OC.
However i noticed something i'm not 100% sure it is right.

I have set my VCore in BIOS @ 1.290v in Fixed Mode but when i get to Windows and run CPU-Z i get shown (as you can see bleow) 1.296v. This 1.296 stay pretty constant when the PC is idle but when i start doing something it goes up to 1.304v.

When i run Prime95 it fluctuates between 1.304v and 1.320v but most of the time it is @ 1.312v.

Pics of both below:

So my question is: Is this fluctuation normal and expected?
I thought by setting the VCore in BIOS at Fixed mode it should stay at whatever i set it to, no?

Do i have wrong understanding of all this?

Thanks

Mookzen · 7 Feb 2012 at 19:01

First of all, power saving features such as C1 and C3/6 like to fluctuate voltages, try turning those off considering they likely don't work properly with a manually set voltage anyway.

Failing that, sounds like load-line-calibration set a bit higher than needed to copensate for vdrop under load, so instead of just giving it some extra juice to maintain the manually entered voltage it ends up with a bit on top. Commonly there is a setting in the BIOS named something like LLC or Vdrop with a range of stages, moving from low to high they either undercompensate or overcompensate the manually set voltage as it drops under load.

Note that I am not familiar with your particular BIOS, it may well be that the load-line-calibration setting only compensates upwards, in that case drop your vcore a tad and increase said setting until you are satisfied with the voltages under load.

In any case, you can use the aforementioned setting to bring the volts down a bit, though a fair share of 2500k at 4.5Ghz will lose stability somewhere around there. Mine refuses to play nice without at least 1.33v under load. (then again it is a rather avarage sample)

xxShinobixx · 7 Feb 2012 at 20:08

Yeah, it was the LLC, i had it set to the highest setting and now that i lowered it down by one notch it even undervolts a little so my CPU is running @ 1.28v under full load. I'm fine with it tho.

Mookzen · 7 Feb 2012 at 20:16

xxShinobixx said:
Yeah, it was the LLC, i had it set to the highest setting and now that i lowered it down by one notch it even undervolts a little so my CPU is running @ 1.28v under full load. I'm fine with it tho.

A very respectable chip seems like, could be 4.8 capable at under 1.4v.