Asus voltage

Hi,
My i7-920 runs at a range of voltages between 0.928V - 1.264V, depending on the C-state of the moment.
I believe there are no less than 7 C-states.
(Intel SpeedStep must be enabled in BIOS to achieve the increased 22x TurboBoost CPU multiplier - and I had thought it only reduced CPU speeds)
So the 920 with vcore auto has very sophisticated power management, and numerous different C-state levels.
I think it still works if you manually adjust voltage in BIOS, it will still change C-states and adjust up & down from there.
Note: EIST function, CPU enhanced halt (C1E), and C3/C6/C7 state support must all be enabled in X58 BIOS to realize full i7 CPU potential.
Some of these may be disabled by default, as not all CPUs will support them, so make sure they are all enabled.
The end result for me is 2.93 GHz most of the time (which is the TurboBoost speed) even with all cores working!
My Gigabyte mobo is very aggressive in this way, and wants to run TurboBoost all the time...
Anyway - for stock speed, all the automatic stuff is yer pal.
For OCing, all the auto stuff will still work....
Except when you cross beyond 150FSB, if you approach ~166FSB and above you will probably have to begin ramping up voltages, and disabling the auto stuff, to maintain stability.
Personally, I'm all default/stock - and it's bloody screaming fast (but still heats up my room like a furnace).
Therefore I have no itch to OC. Heat is The Enemy,
Regards

I dont really know the answers to your questions but i'm gonna answer anyway  

About the Asus mobo being able to drop vcore when running an overclocked cpu, I'm not 100% sure but considering I used to have an Asus P45 mobo that was able to do this I would say yes. You want to look for a 'vcore offset' option in the bios. Gigabyte mobo's have this feature as well (called 'dynamic vcore'). MSI i'm not sure, their P55 mobo's dont seem to have it.

Your second question is interesting but I dont think it would be possible to answer without measuring the actual power use. And then it would depend on your usage as well. Most likely with the auto voltage option you will have even lower vcore during idle but the question is to how much power saving this actually translates. Your cpu seems to be able to run on a very low vcore (you sure its really really stable?) so that would definately save quite a bit during load.

While an interesting question, what you could do with a motherboard that has the feature you're looking for is combine the best of both worlds. With dynamic vcore you would be able to specify an offset value which can also be negative. So lets say your cpu uses between 0.8V and 1.2V idle/load using the auto setting. You were able to run your cpu stable at about 1.0V so you could set vcore offset to -0.2V. This would then drop the idle voltage as well to 0.6V.

With either EIST, C1E or C3/C6/C7 enabled will vcore lower in idle. Only when EIST is enabled will the multiplier drop as well. Vcore will only drop when you use the auto or dynamic vcore setting, when you use a fixed value vcore will not drop during idle, regardless of the energy saving features enabled. With EIST enabled only the multiplier will drop but not the vcore. At least that's how it works on my mobo. When using a mobo that doesn't offer a dynamic vcore setting the only way to have vcore lowering during idle is to use the auto setting, but since most mobo's like to overvolt this will limit your overclock or have a negative impact on power usage.

As for the post above mine, I'm a Lynnfield not a Bloomfield user so things might be different but I have to say that EIST is not necessary to use the full turbo mode with my cpu, only C3/C6/C7 states need to be enabled. If I disable EIST while Turbo and C3/C6/C7 are enabled, my multiplier will change between x24 in idle or when no more than 2 cores are used and x21 when 3 or 4 cores are used. When I disable C3/C6/C7 the highest multiplier is x21 (this makes sense since to use the x24 turbo multiplier unused cores must be deactivated and C3/C6/C7 does just this). Disabling or enabling C1E has no effect on turbo at all.

Hmmm, your Lynnfield only goes to 24x when idle.........

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Yes, but it doesnt bother me too much considering it's an i5 750