Bitcoin Forum

I mining LTC, but posted here because the type of currency irrelevant anyway.
I recently saw somewhere in a forum how to undervolt the 7990, but can not find that post now. I just remember that I have to change some values in registry to zeroes, copy dll to afterburner directory and so on.
I will really appreciate if somebody would give me a link to that post or just let me now what I need to do.

The card I bought makes easily 1200 and more despite I lowered GPU and memory clocks, so I want to undervolt it to keep temperatures in the range I am feel comfortable with.

Thanks in advance.

Is it really worth mining with a graphic card anymore?
you are getting 1,200 Mh/s but you are talking about 550W just for the video card + computer makes ~700w
at $.10 Killowatt hour you are spending $47 a month on electricity.

You would be better off buying Erupters and using a Raspberry pi & a blue/red furry or 4 Erupters.
The Pi cost $45
Erupters (Crazy price now but I got mine for $10-15)

so in 2 month of electricity you could have a pi running 4 Erupters (depending on price) and get the same performance and spend 15w $1.01 a month on electricity.

Gee, I knew somebody would respond like this...
If you read careful, you will see I don't mine bitcoins, so yes, it is profitable. Also, as I said, it is irrelevant to the question I ask.

Sorry.

I have a 7950 and you can download afterburner and you just need to change the settings in the config file of the afterburner software then you can change your voltage to what ever you want.
I have done that one mine. I will look and see if I can find the how to.

What kind of 7990 do you have? is it modified or is it the AMD Reference one?

Thank you for you trying to help, but as you can read my post, I know about afterburner. It would not change the voltage of my card unfortunately that easy and some changes should be made in registry. I hope somebody who did changes I am talking about will help.

http://www.newegg.com/Product/Product.aspx?Item=N82E16814131493

Ok I found it.

So MSI afterburner will not change Voltage on crossfired video cards (Yours is 7970 crossfire)
You need to Disable ULPS in the registry

Here is how to do it:

Go to registry and disable Ulps:

[HKEY_LOCAL_MACHINE\\SYSTEM\\ControlSet001\\Control \\Cl ass\\{4D36E968-E325-11CE-BFC1-08002BE10318}]

and change "EnableUlps" to 0 under the 0000 and 0001 or 0003 keys.

http://www.overclock.net/t/667144/crossfire-disabling-ulps (http://www.overclock.net/t/667144/crossfire-disabling-ulps)

Once that is done the mofified Afterburner should work.

To enable the unofficial overclocking in this version it is necessary to edit the MSIAfterburner.cfg file located in the installation directory of AfterBurner (typically Program Files (x86) MSI Afterburner):

You need to alter the following:
Seek UnofficialOverclockingEULA field and add following text:
I confirm that I am aware of unofficial overclocking limitations and fully understand that MSI will not provide me any support on it
Set UnofficialOverclockingMode to 1 to keep PowerPlay active (may not work on old ASICs), 2 to traditionally disable PowerPlay or to 0 to temporary disable unofficial overclocking path
Using the unofficial overclock method opens up more freedom in terms of voltages and clock ranges, it however also can open a can of worms in terms of stability or weird issues.

Unofficial means unsupported -- we grant some extra tweak options to fool around with, but in no way, manner or fashion is it supported by Guru3D.com or MSI.

From: http://forums.guru3d.com/showthread.php?t=338906 (http://forums.guru3d.com/showthread.php?t=338906)

Thanks!

Or you can just use new MSI Afterburner BETA with ULPS support ;)

Well, I tried to change voltage with version 17 beta, but still no luck.
Did not try to change registry yet, did not have a time (before doing so I want to backup drive's image first). 

I had a xfx 7990 2 card wide version my problems was keeping it cool. Just keep an eye on your temps because I think I warped mine and I had to RMA it. I was able to undervolt with msi afterburner. Stable I was able to run mine at 1450 mhs @99C. ;D

I don't try to make it most from it, despite it is running in the cooled server room. It runs with average about 1200 KH/S (scrypt) and temperature around 81-83C. I just checked pool and it shows 1594 in the particular moment. I noticed that sometime load of the card changes and card load shows only 90-91%, of course when its happened hashing speed falls pretty much, temperature also falls up to 69C. I had a feel that it is pool problem. It does not looks like throttling, cause temperature is not high. And sometimes speed is really up (just checked again and it shows 1440). Also I noticed that speed falls when I open TeamViewer, but probably it is coincidence. Memory on board is 4GB and I did not noticed any improvement after 2MB.

What is do is the following
a) set voltage to 0.9v using cgminer
b) set clock to 700
c) set memory to 1200

works a charm with 7990.

Dude, sorry, I know how to set voltage with cgminer, the thing is that it does not change it, looks like it is locked.

I am assuming that you are using the MSI Afterburner Beta and you have ticked  the three boxes in the General tab. I didn't so if you did you are a better man than I  :D

What card and BIOS version are you running as some cards BIOS will not change voltage and some say that they have say they have but don't?

You have to downclock to 700MHz for voltage to get reduced to 0.95V

What hashrate do you get with those settings? (Litecoin obviously)

Don't want you to feel bad, but yes, I ticked those boxes (but because I read about that in some post before, not because I am smart)

I undervolted my XFX R7990 last night and I have to say, woohoo!  Mining scrypt coins.  Used  MSI Afterburner beta (I think it was rev 18).  No modifying files or anything necessary.

I was getting the throttling on gpu0 anytime I put the card under load.  Hash rate with core clok at 1000Mhz and memory at 1500 Mhz was 1.15 Mhash combined (roughly 650 khash on gpu1 and 520 khash on gpu0 due to throttle). Stock voltage 1200 mV.

Underclock to 1070 mV, core clock 1000Mhz and memory at 1500Mhz.  No throttling anymore and now averaging 1.3 Mhash with no issues.  Haven't tried tweaking anything yet to see if I can improve that more.  Stock fans/cooling and both gpu's run from 65-67 degrees C.

it looks like your video card allows to change voltage. I could not change the voltage, but i don't want to change firmware. So I have average 1180 KH/S (could have a bit more, but don't want to push card to higher temperatures).