8600M GT and Nibitor undervolting.

I attempted to undervolt my GPU this morning, and when I read the GPU BIOS with the latest version of Nibitor, I noticed something strange.

In the voltage tab, I see only 3 voltages, "2D" (1.0V), "thrtl" (1.15V), and "3D" (1.2V). The "Extra" field is grayed out.

I understood "extra" to be a performance mode, (the voltage that would run in intense 3D gaming), is this correct?

Anyway, because of this problem, I tried to undervolt by changing the default VIDs (1.0, 1.15, 1.2, and a mysterious 1.35 that I can only assume belongs to the "extra" setting).

BUT, when I undervolted the 1.35 VID to 1.2, I got no temp decrease, leading me to believe that maybe "Extra" doesn't even come into play on the 8600M GT..

Any thoughts?

 

theres a program you can use to re-enable blanked off check boxes aslong as the underlying software is there to run, I just cant quite rember its name off the top of my head I used it when changing the product ID of my n95 if I find it I'll post it then we can see what perf. mode does

 

The "Extra" row is grayed out in mine as well, in both the Clockrates and Voltages tabs. I hadn't actually noticed it before - the guide I was looking at didn't mention it. According to Google it's a new mode added with GeForce 8 that does...something or other. There's no real definitive explanation. However, I was able to garner two things:

*The 8600M GT definitely is not underperforming with "Extra" disabled. This is from personal experience - I've been using my 8600M GT for more than a year and the 3D settings (which are what I can modify in nTune) are definitely serving me well and giving the expected performance.
*Enabling the "Extra" mode may cause programs to not be able to read clock speeds of the GPU. Not sure why that is but that isn't a desirable effect.

So it doesn't seem to me that Extra mode is especially beneficial. The only thing I can think of is that it allows you to increase the voltage to 1.35V - I am unable to even see a 1.35V option on mine, perhaps because Extra is grayed out. That 1.35V might give you a slightly better overclock, but would generate quite a bit more power consumption (26% from the voltage change with no additional overclock) and thus heat.

But it definitely doesn't seem like something you need to enable to undervolt.

At any rate, post your stable voltages here when you find out what they are. I've been pondering undervolting my GPU, but decided to play it cautious. Mine runs at 1.15 2D, 1.15 Throttle, and 1.20 3D by default. I'm thinking dropping down to 1.18 on 3D ought to work. Even 1.15 might but this isn't something I feel like pushing. And it seems 1.0 should work on 2D, no? If yours has always been 1.0 then I see no reason why not. And that would save a lot of power at idle - about 25% of what the GPU consumes.

Clock speeds are 475/400, 275/200, 170/100 at 3D/Throttle/2D Core/Memory, respectively. I software overclock 3D to 562/400, and underclock 3D to 118/100 depending on what I'm doing (and yes I know underclocking 3D is quite useless for saving power on the desktop).

I'll be looking forward to seeing what else you may discover and what voltages you use if you decide to go ahead with this - and of course the results from such voltages.