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It seems that, although it's simple in Windows w/ Afterburner, you cannot UNDERVOLT under BAMT/Linux. I mean you can, but it's not applied, even if it's reported as applied, neither with atitweak, neither with cgminer.
I mean you can undervolt, but it's useless because there are some frequency thresholds and if you set frequency greater than threshold for a voltage, voltage automatically goes to the next respective voltage. The thresholds are:
    0.85V -> 450MHz
    0.90V -> 600MHz
    0.95V -> 700MHz
    nominal voltage -> unlimited frequency to at least 1210MHz (I could not try more).
I'm pretty sure about this behavious, I have tested with both GPU-Z under Windows, and voltmeter on GPU voltage rail and clampmeter on video card power supply wires under Linux.
To add insult to injury, you cannot modify the BIOS, it seems there's a checksum nobody knows how to compute.

Now, why I would want to undervolt? Lets say I'm able to undervolt 10%. I'll loose around 10% maximum frequency (hashing rate). But I'll made around 30% power savings (21% from voltage drop, 10% from frequency). So, with only 10% lower hashing rate, 30% power savings, and much lower noise.

But there might be a way. It looks like 7970 nominal voltage can be one of the following:
    1.175V = ASIQ quality <75
    1.112V = ASIQ quality between 75 and 80
    1.050V = ASIQ quality between 80 and 85
    1.025V = ASIQ quality between 85 and 90
So, in theory, if you write a 1.025V BIOS on a 1.112V card and it works, like I want to do, you'll make a 8% undervolt.

Can somebody help me with a 1.025V BIOS for MSI R7970-2PMD3GD5?
(on www.techpowerup.com there's only one BIOS for my card :( )

In Windows, ASIC quality can be obtained with right click on GPU-Z title bar. BIOS can be dumped from GPU-Z also.

Silly question but did you try rebooting after saving your settings?
Some things on Linux don't get applied until the boot scripts run.
Can be a bit of a hassle if you underclock it enough to stop it rebooting though.  ::)

You cannot directly software undervolt 7970s on linux.

You may undervolt on windows, and then reboot to linux. I think as long as power doesn't go off, it will keep the setting.

I succeeded in undervolting on linux/bamt.  ;D ;D ;D ;D
I running now with 7970 at ~4.8Mh/J on reduced voltage versus ~3.2Mh/J on stock voltage.  ;D ;D ;D ;D
I'll make next week a separate thread in case somebody's interested.

Although I haven't tried I believe you're right... but it's too much complicated if you have many rigs.

Great! I'm curious, how did you do that? I hope it wasn't afterburner with wine..  :P

yeah very curious. how did u manage to uv on Linux.

I have modified the BIOS, but... it is not straightforward :)

hmm, did u digitally sign the bios? I have tried umpteen times to obtain lower voltage bios from powercolor support, but no fish.

I have obtained only one point of undervolting (obtaining ~540 Mh/s at ~110W) and I have to work a little more to see how much I can extend my ideea. I'll post again in a few days when I'll finish.

waiting. good luck!

yes, please, inform us :-)


I have:
1 PowerColor HD 7850 (AX7850 2GBD5-DH) 85.3% ASIC quality
1 XFX R7970 DD (FX-797A-TDFC) 68.6% ASIC quality

what to do to undervolt?

what was your result?


threads about my undervolting questions:

• 7850 https://bitcointalk.org/index.php?topic=392098.0
• 7970 https://bitcointalk.org/index.php?topic=395004.0

I just want to announce SUCCESS :-) I did it!
Undervolting XFX 7970 DD by tweaking the original BIOS;
amazing results, saving 1/3 energy!

Instructions here:
https://bitcointalk.org/index.php?topic=395004.msg4282261#msg4282261

 8)

http://cdn.overclock.net/8/89/89350c26_7970-after-flashing.png