Can someone explain offset voltage to me?

[Markbnj]

I have my i5 2500k running at 4.2 at about 1.28v. I'm waiting delivery of an Evo cooler so that I can work on getting it into the mid-4's with reasonable temps. Currently I'm using manual CPU voltage, and the vcore stays pegged at 1.28 even when the chip speedsteps down to 1600. I've read about using the offset voltage setting to adjust the vcore based on the CPU frequency, or something like that. Can someone explain how this works? I have an Asus P8P67 Pro rev. 3.1 if that helps with settings nomenclature. Thanks!

 

[Accord99]

On an Asus motherboard, you normally need to use the Auto voltage setting to take advantage of decreased voltage during idle. However, the MB will then automatically choose a voltage based on the clock speed of the CPU, increasing higher with clock speed. The Offset value allows the Auto voltage to be tweaked; typically for a mid 4 GHz overclock, the MB's Auto voltage will be higher than necessary so you would use a negative Offset value.

For example, on my P8P67 Deluxe and 2600K, at 4.8 GHz the core voltage reaches 1.49v with full CPU load. But testing shows that the CPU is still stable at around 1.38v, using an Offset of -0.11v allows me to limit the maximum voltage to about 1.38v. Though, you probably need to enable the C1,C3, etc power settings in the BIOS as I find they are also required to get the CPU to drop to a lower voltage at idle.

 

[Idontcare]

Are you looking for someone to explain what it is or for someone to explain how to effectively use it in overclocking your specific setup (mobo)?

If you are looking for help with OC'ing on your specific mobo you are probably more likely to find other experienced users with your mobo by posting in the mobo forum.

 

[cantholdanymore]

Just happen to have this in my bookmarks, by asus themselves:
http://rog.asus.com/forum/showthread.php?2162-Overclocking-Using-Offset-Mode-for-CPU-Core-Voltage

 

[Grooveriding]

Just happen to have this in my bookmarks, by asus themselves:
http://rog.asus.com/forum/showthread.php?2162-Overclocking-Using-Offset-Mode-for-CPU-Core-Voltage

Useful post there.

Offset mode is really nice because it lets your voltages reduce at idle when you are overclocking. Keeps idle temperatures way down. For reference using offset my cores idle at 28-31 or so, without they are 38-41.

One thing I do find is using offset holds you back from getting the best possible overclock. I can do 4.8 stable without using offset, but with offset I cannot get 4.8 stable without using way too much voltage because of the way offset defines your voltages.

 

[Idontcare]

Offset mode is really nice because it lets your voltages reduce at idle when you are overclocking. Keeps idle temperatures way down. For reference using offset my cores idle at 28-31 or so, without they are 38-41.

That's interesting, its obviously going to be user-dependent because no two people's "idle" is the same given the background levels of activity won't be the same unless the rigs are configured identically.

For example, on my rig my idle temps are at most 3C difference between using offset versus manual Vcc modes.

Power-gating on idle really ought to be negating the power-consumption differences at idle unless you have so much background processing going on (or you've disable all your power-saving features in the BIOS?) that powergating is never in play.

 

[Kenmitch]

That's interesting, its obviously going to be user-dependent because no two people's "idle" is the same given the background levels of activity won't be the same unless the rigs are configured identically.

For example, on my rig my idle temps are at most 3C difference between using offset versus manual Vcc modes.

Power-gating on idle really ought to be negating the power-consumption differences at idle unless you have so much background processing going on (or you've disable all your power-saving features in the BIOS?) that powergating is never in play.

I think this would also be cooler dependant at the same time. The more efficient the cooler the lower the idle temps will be no matter what the voltage at idle is. If a not so good cooler is being used or a person has a case without good airflow then I could see having a pretty good split between idle at locked vcore vs idle using offset vcore.

Your still using the lapped H100? Or did you change it for something else?

 

[Grooveriding]

That's interesting, its obviously going to be user-dependent because no two people's "idle" is the same given the background levels of activity won't be the same unless the rigs are configured identically.

For example, on my rig my idle temps are at most 3C difference between using offset versus manual Vcc modes.

Power-gating on idle really ought to be negating the power-consumption differences at idle unless you have so much background processing going on (or you've disable all your power-saving features in the BIOS?) that powergating is never in play.

Well the main issue for me is if I do not use offset my voltage does not reduce at idle. So my chip is being fed 1.385V at idle, my clocks do reduce, but the voltage remains at load levels.

If I use offset, at idle my voltage goes down to .936 with the large temperature reduction to go with it. I've played with eist, c1e, speedstep etc; using a manually punched in voltage and none of them allow my voltages to reduce at idle.

FWIW my motherboard also only allows increments of .005 to be used for offset, so that causes my issue trying to run 4.8 with offset voltages. I have to increase the offset by an increment that goes above what my chip needs to be stable, giving it too much voltage for my liking. So I run at 4.7 using a lower offset than what I need for 4.8.

I also notice offset seems to even at load fluctuate in the amount of voltage it delivers. Generally I see about 1.38 or so, but running linx, it feeds my chip 1.395. My board has auto,normal,high,ultra high, extreme for LLC levels and I run using the High LLC. I need to play with it some more as the different LLC levels affect load voltages drastically. Just too many dang options on this board, wish I had more knowledge of what it all does.

 

[Idontcare]

I think this would also be cooler dependant at the same time. The more efficient the cooler the lower the idle temps will be no matter what the voltage at idle is. If a not so good cooler is being used or a person has a case without good airflow then I could see having a pretty good split between idle at locked vcore vs idle using offset vcore.

Your still using the lapped H100? Or did you change it for something else?

True, my observations may be caused by a superior cooling rate (lapped 2600K and lapped D14 at the moment) compressing the range of idle temps for the given range of idle voltages. Very true.

But still, power-gating is supposed to basically eliminate all of the voltage induced leakage losses regardless the voltage. But that is only true if power-gating is actually being effected by the CPU's PCU.

Well the main issue for me is if I do not use offset my voltage does not reduce at idle. So my chip is being fed 1.385V at idle, my clocks do reduce, but the voltage remains at load levels.

If I use offset, at idle my voltage goes down to .936 with the large temperature reduction to go with it. I've played with eist, c1e, speedstep etc; using a manually punched in voltage and none of them allow my voltages to reduce at idle.

FWIW my motherboard also only allows increments of .005 to be used for offset, so that causes my issue trying to run 4.8 with offset voltages. I have to increase the offset by an increment that goes above what my chip needs to be stable, giving it too much voltage for my liking. So I run at 4.7 using a lower offset than what I need for 4.8.

I also notice offset seems to even at load fluctuate in the amount of voltage it delivers. Generally I see about 1.38 or so, but running linx, it feeds my chip 1.395. My board has auto,normal,high,ultra high, extreme for LLC levels and I run using the High LLC. I need to play with it some more as the different LLC levels affect load voltages drastically. Just too many dang options on this board, wish I had more knowledge of what it all does.

Yeah that sounds more like your LLC settings are driving the observed voltage variability than anything else (offset/manual modes).

I don't use offset because I actually undervolt my chip at nearly every multiplier, the VID table is just way to aggressive. But if I undervolt by way of offset mode then the idle voltage is also way to low and my rig spuriously crashes when idling.

Going to manual mode was the only way to address this without raising my loaded voltages ever higher just to account for idle volt instability.

That said, this MIVE-Z is like dead-nuts on for Vcc supply at the default (auto) LLC setting, confirmed with a voltage multimeter, so that may be what my $360 gets me in terms of mobo capability?

 

[Markbnj]

I don't use offset because I actually undervolt my chip at nearly every multiplier, the VID table is just way to aggressive. But if I undervolt by way of offset mode then the idle voltage is also way to low and my rig spuriously crashes when idling.

Interesting. That was going to be my next question after reading the first few replies. If the same voltage offset isn't stable at different processor frequencies then that's a real problem. I need stability at all times and at all power levels.

I'm off to read that Asus post. Thanks for the input, guys. Btw, what's the typical process for finding the right offset? Bump the multiplier with the voltage on auto and see what the system chooses, then adjust down until instability?

 

[Markbnj]

Just happen to have this in my bookmarks, by asus themselves:
http://rog.asus.com/forum/showthread.php?2162-Overclocking-Using-Offset-Mode-for-CPU-Core-Voltage

An awesome post that answered everything. Thanks a bunch!

 

[Puppies04]

I don't use offset because I actually undervolt my chip at nearly every multiplier, the VID table is just way to aggressive. But if I undervolt by way of offset mode then the idle voltage is also way to low and my rig spuriously crashes when idling. Going to manual mode was the only way to address this without raising my loaded voltages ever higher just to account for idle volt instability. That said, this MIVE-Z is like dead-nuts on for Vcc supply at the default (auto) LLC setting, confirmed with a voltage multimeter, so that may be what my $360 gets me in terms of mobo capability?

Does your board let you raise the minimum processor speed, if I had this problem I would just raise it a little so it idled at say around 2-3ghz (whatever stops it crashing) instead of 1.6