AMD Radeon HD 6990M Voltage

I want to OC the 6990M CFX setup that I have in my R2. I have a few questions beforehand though that I think some people on here probably have the answers to:

1. Do these cards require a BIOS flash in order to change voltages? When I installed them after first replacing my 5870M CFX, I undervolted them a tad, listening to the advice I got on this forum.

2. What OC utility is typically used for OCing these? I looked at AMD Overdrive in CCC, but it appears to have a super-conservative governor on the clock speeds, which may or may not correspond to my slightly lower voltages. I tried to install MSI Afterburner and had to hard reset, so I'm guessing that's not an option.

Any info much appreciated. Trying to eek out some more performance out of the good ol' R2 while I wait on some desktop upgrades

 

Not sure about the voltages, but for overclocking I prefer TriXX:

https://www.sapphireselectclub.com/ssc/TriXX/

 

Okay that answers one question Also looks like voltages are configurable with the software. I guess the question now is how far I can push them and on what voltage...Maybe someone who has experience ocing these can offer up some conservative starting points?

 

The only way to lower the voltage is to flash the vbios as far as I'm aware - that's how I've been doing it.

To increase the voltage you have to do a hardware mod to the vrms on the card itself - something which I'm in the process of doing. With the hardware mod - it seems like you can push it to around 940mhz on 1.175v - on the stock 1.100v the cards top out around 840mhz.

 

http://forum.notebookreview.com/ali...-flashing-vbios-may-work-other-gpus-also.html

This is my write up for a 7970m, mighjt also work with a 6990m although people seem to have trouble with syncing the first card and second card voltages. You might have some luck with it though, as far as I know this is one of very few ways to actually change voltages without VBIOS flashes.

 

I followed your guide, but after adding -xcl to the target address I never got a pop-up. I restarted anyway, but no OV option in Trixx as far as I can tell.

 

did you add a space? if you don't put a space there it won't work.

I didnt get the pop-up at first, I had to minimize and maximise it a few times and play around with it, I think you have to exit the properties window too.

 

Yes I added a space.

I went back and got rid of the -xcl, hit apply, hit okay, and then opened up the window again and added it, hit apply, and hit okay. Repeated the process about 10 times and couldn't get a pop-up to appear. I'm running Windows 8 Pro 64bit if that makes a difference. My build is in my signature.

 

I am not too sure because it has only been tested so far on people with 7970m's. Could very well have locked voltage adjustments.

 

VDDC is the voltage adjustment slider I believe. Now just to try it...

 

Okay I've tried the voltage adjustment slider and it doesn't seem to be doing anything good...Tried to up the voltage to 1.0v from .96v and got a BSOD. Each .1v I upped it before that didn't crash it, but didn't solve the scrolling on my screen that I usually associate with not enough voltage to sustain the clock speed. I guess they have to be flashed.

Now the question is: With an OC from 3.1Ghz to 3.5Ghz on my 940xm and these two 6990m in my r2, is the power supply beefy enough to sustain OCs on both??

 

Try moving it up to around 1050. Even 1075. The worse thing that will happened is that you BSOD.

 

BSOD'd. Not off the bat though. Not scrolling, no instability on first card when I increased the core clock to 775Mhz and the mem clock to 1000Mhz. This was on 1.050v. As soon as I tried to increase the voltage on my second card though, instant BSOD.

 

Sounds like its a power supply issue... you would need at least a 330W one i would think.

 

Ya I'm thinking that's the issue. Do larger PSUs compatible with the M17x R2 exist? I'd buy one in a minute.

 

That is something you'll have to find out haha, I know 330W is the biggest one alienware make but not sure what it is you have, and what is compatible.

 

Meh, for now I'd just like to get maybe 50mhz more out of them, which I'm sure isn't impossible on stock voltage. I'll play around with it a bit.