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Manual vs Offset voltage control

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  • CPUs
  • Overclocking
Last response: in Overclocking
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a b à CPUs
August 11, 2012 8:52:37 PM

Hi everybody,

Can someone explain how voltage control works, and in particular, how manual control differs from offset?

I understand that most "real life" overclockers prefer offset. This is because the voltage scales with the CPU speedstep and thus adjusts the voltage (and hence heat and power consumption) depending on CPU load. My system (the relevant parts of it) is: i7 2700k, Asus P8Z680 Deluxe/Gen3, 2xGTX 680, Noctua N-D14 cooler.

Here's my issue. I want a liveable system for general use as well as performance oriented tasks. I have overclocked the CPU to all four cores max turbo 4.84 GHz (103*47), in order to maximise performance when I need it. I prefer to just "set and forget" and use the same BIOS settings whether I'm gaming, working, browsing, video editing, transcoding, whatever.

I'd really like to use offset because this allows the voltage (and hence heat and power consumption) to scale with load. Under manual voltage control, voltage seems to adjust with load a bit, but in a much narrower range.

The problem is this. When using the offset mode, if I set it at "Auto - by CPU", it scales to a crazy voltage under load. When running Prime95 the voltage goes up to 1.6V (and the temperature goes up to 85 degrees). This is obviously far, far more than necessary and unacceptable for a Sandy Bridge CPU so I quickly shut it down. However, if I set the smallest negative offset of -0.005V, my computer blue screens on start up without fail.

There seems to be no offset voltage setting that will boot into Windows without blue screening, that doesn't also scale to an excessively high voltage under load.

I therefore seem to be stuck with manual control - I have set the manual voltage at 1.36V. This boots ok and seems to be stable under load with all 4 cores at 4.84 GHz. Under load, temperatures hover around 65 degrees, which is fine and the voltage increases to 1.392V. (The fact that it is stable at this voltage proves that my voltage scaling under offset mode is completely crazy and unnecessary).

So if manual control works, what's the problem? Well, as I write, the CPU voltage is 1.378V. I am not doing any background tasks, just writing this post. It works but is far more than necessary. I like to leave my computer idling for long periods of time, but at this voltage it's using far more power than necessary.

The solution would appear to be offset voltage control but with a sensible scaling factor. Is there something else in my BIOS settings that can affect the scaling factor? Eg Load Line Calibration? Or do I just have to accept that at my multiplier settings, I will never get offset voltage control to work?

Any help or insight much appreciated.

More about : manual offset voltage control

a c 78 à CPUs
a b K Overclocking
August 11, 2012 9:10:51 PM

Try backing off the speed a bit and then using an offset.


You may just be at a speed that's stable with constant voltage but unstable with an offset approach.
a c 283 à CPUs
a c 110 K Overclocking
August 11, 2012 9:15:47 PM

You need to use a + offset. Just an example, since offsets will never be the same for any two chips, but a +.020 offset gives my 2500K a Vcore of 1.328V at 4.5 (idle with the High Performance power plan enabled. It still lets the voltage drop with the Balanced power plan active).

A very nice guide to OC'ing with offsets. http://rog.asus.com/forum/showthread.php?2162-Overclock...
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a b à CPUs
August 11, 2012 10:01:35 PM

Z1NONLY said:
Try backing off the speed a bit and then using an offset.


You may just be at a speed that's stable with constant voltage but unstable with an offset approach.


Thanks, yes, it works at lower clockspeeds.
a b à CPUs
August 11, 2012 10:03:51 PM

DJDeCiBeL said:
You need to use a + offset. Just an example, since offsets will never be the same for any two chips, but a +.020 offset gives my 2500K a Vcore of 1.328V at 4.5 (idle with the High Performance power plan enabled. It still lets the voltage drop with the Balanced power plan active).

A very nice guide to OC'ing with offsets. http://rog.asus.com/forum/showthread.php?2162-Overclock...


Thanks, I'll read the guide. Just for clarity, I assumed that a - offset reduces the voltage while + offset increases it, is that correct?
a c 283 à CPUs
a c 110 K Overclocking
August 11, 2012 10:09:08 PM

bwrlane said:
Just for clarity, I assumed that a - offset reduces the voltage while + offset increases it, is that correct?


Correct. :)  As the guide says though (I believe), it's based off of your CPU's VID, and a + offset isn't linear (a +.005 offset doesn't necessarily add 5mV), so it takes a bit of trial and error to get right.
a b à CPUs
August 11, 2012 10:29:43 PM

DJDeCiBeL said:
Correct. :)  As the guide says though (I believe), it's based off of your CPU's VID, and a + offset isn't linear (a +.005 offset doesn't necessarily add 5mV), so it takes a bit of trial and error to get right.


Ok thanks, will experiment a bit. However, my problem is that with a zero offset (ie default VID) it seems to go up to 1.6V under load (with crazy temps). This suggests to me that I should set a negative offset, but even the smallest negative offset (5mV) results in a blue screen when booting.
a c 283 à CPUs
a c 110 K Overclocking
August 11, 2012 10:36:31 PM

bwrlane said:
Ok thanks, will experiment a bit. However, my problem is that with a zero offset (ie default VID) it seems to go up to 1.6V under load (with crazy temps). This suggests to me that I should set a negative offset, but even the smallest negative offset (5mV) results in a blue screen when booting.


Yeah, that happens to me as well. Auto voltage is just like that, but trust me that a + offset will be lower.
a c 78 à CPUs
a b K Overclocking
August 11, 2012 10:38:53 PM

bwrlane said:
Thanks, yes, it works at lower clockspeeds.


You may want to back off the speed enough to give you some room to work.

Find a speed that's slow enough to be stable with the offset (and resulting max voltage) you want to use.

Then start bumping the speed in small increments and ensure that the voltage doesn't creep up too much as you increase speed. (You may have to increase the negative offset further to stay under your desired max voltage)
a b à CPUs
August 12, 2012 1:01:01 AM

Thanks for your replies folks. After a bit of experimentation I've had some measure of success.

Load line calibration had been set at extreme. I guess this was causing the ridiculous voltages (and hence temps) when running under load. I have now set it to the lowest level (regular) and it now works.

With offset voltage (with a zero offset), the voltage seems to top out at about 1.45 under Prime95 at 4.84GHz. The temps are in the high 60s, occasionally hitting 70, which I guess is ok when the CPU is fully stressed.

I still don't see why the voltage needs to auto-adjust to 1.45 volts when it seems to work perfectly well at 1.39. But in manually setting the voltage at 1.39, I lose the ability for the CPU to reduce voltage when idle (which is most of the time).

Nevertheless, I've found a way of using offset voltage that has the joint benefit of a) not blue screening when Windows boots (which happened if I set a negative offset) and b) not ramping up to 1.6 volts under load (which happened if I set a zero offset) and c) reducing voltage when CPU performance is not needed (which is the whole point of using offset).

The load line calibration setting was at fault.
!