UV and UC of 7970M at 2D clocks; findings.

As nobody has seemed to try this I decided to undervolt down to 0.75V and 200/150mhz today in order to boost battery life as much as possible in my M15x and lower idle GPU temps to the max.

I used SLV7's vbios patcher. Anyways the 7970M does not allow for a lower voltage than 0.8V. Even though I selected 0.75V it only took it down to 0.8V. This is a little disappointing but still an improvement over 0.825V. The core underclock worked no problem.

At 150mhz ram speed 300mhz core is completely bottlenecked. There is no point running it at this speed 200mhz won't therefore make much difference to 2D performance. I know to most running enduro these findings mean nothing but I thought I would post it up for those in the same boat as myself.

 

battery life how much longer?

 

I can't say about battery life. Not a lot. Talking 0.8V vs 0.825V. However at idle the card now runs just 35C instead of 38C. This in ambient of 25C+

If you have the 7970M as a dedicated GPU with no igpu then there is no harm at all in setting the card to 0.8V and 200mhz core. Idle temps WILL be lower which also means potentially gaming temps are lower as it gives the cooling more initial pre-gaming cooling capacity.

A good thing to learn here is that the card is hard coded not to go lower than 0.8V so no point selecting any value lower than that in the vbios patcher.

 

FYI, this is due to the hardware safeguarding of the LDO regulator the manufacturer uses on the card. AMD designed/used a certain voltage regulator that has a floor limit that will allow an X amount of voltage to pass through to the GPU core regardless of what the VBIOS dictates to ensure it meets the minimum recommended power input to function as designed. This is to prevent GPU 'blackout'.

 

I thought it was something along those lines. Thank you for the technical description though