Quote from: camaro69327 on May 02, 2013, 10:51:08 PM

Quote

I already have 8 GPU working on identical supporting hardware and OS, aside from 11.12 driver, but this is also with radeon 5000 series and not 7000 series.

8 - 5000 series cards on the same type of Power supply as 8 - 7000 series cards is never going to work.

What Power supply is this your using that can power 8 7000 series cards?? and what are you using to plug them all in ...Adapters?...Duel power supplys?

I'm not going 8 7970. I'm doing 6 due to PCI-E slot quantity limits. I am also undervolting. I use Rosewill Lightning 1300W. Power supply is not the issue here though. I just need all 6 -installed correctly-. If and when power becomes an issue, then I will address it. I highly doubt it would cause driver issues though, especially when all of the cards are IDLING.

Quote from: brucemangy on May 02, 2013, 10:52:51 PM

The 7900 have more video memory ... could be the reason.

Could you mix 5800 and 7900 ?

I was in the process of doing this as a compromise before I even saw your post. The bounty is for 6 7970 in a single windows machine though, and not for a compromise.

Quote from: brucemangy on May 02, 2013, 10:59:57 PM

Quote from: brucemangy on May 02, 2013, 10:52:51 PM

The 7900 have more video memory ... could be the reason.

Could you mix 5800 and 7900 ?

Explanation :
Theory : the BIOS has to address all the video memory ... with 8 58x0 (8x 1 GB) was still ok ...but with 79x0 ... 8x 2GB (maybe 3) ... it is too much to handle.
Worth the try... that would explain the different behaviour ...

Possible, but numerous people have also told me they have 6 7970 on linux, as well as spotting a couple pictures with 6 79xx cards per motherboard. It's definately not a hardware limitation, but a software limitation or badly wrote software. I have a couple problems with this solution though. 1: I have never touched linux before. 2: There are no solutions that I'm aware of that allow you to significantly underclock RAM and significantly undervolt the GPU core. If ADL on Windows (which is what cgminer uses for over/under clocking/volting) is anything like ADL on Linux, it can't underclock RAM more than 150 below core, and I am unable to change the volts at all on my 7970's with ADL. They are reference though and I am able to undervolt with utlilities such as MSI Afterburner and Sapphire Trixx. Afterburner also lets me underclock memory significantly.