dual card 6990 and 6970 won't work - advice needed! (SOLVED)

[organofcorti]

I'm a multicard noob, please be nice.

I just received a stock reference 6970. I have a 6990 which I've used for a while. Neither card are OC.

I've tried using both on Linux and Windows. With each card separately they work fine, no problems. Together, my they wont play nice!

Windows - I can get in to my user account. If I only boot up using one gpu I'm fine, and I can run guminer fine. If I then boot up the other gpu by swapping monitor leads I get BSOD. If I start with both gpus attached, I get BSOD immediately I start guiminer.

Linux (linuxcoin 0.2a ) -  boots up, gets to the penguin and coin logo, but then I get a black screen, no X, no cli.

I have:
1 30gb ssd
bluetooth keyboard and mouse
ASUS m4a89tb mobo
sempron single core
Corsair TX 850 PSU
2gb ram

I'm guessing from my symptoms that my psu isn't up to it, but from my noobish calculations I thought 850 watt would have been fine. I've seen similar questions in other posts, and 850 watt seemed ok there too.

Any ideas? Anyone successfully running a 6990 and a 6970 on an 850 watt psu?

Thank in advance  

[airdata]

do you have a dummy plug in the secondary gpu?

I think your psu should be sufficient. 

[organofcorti]

do you have a dummy plug in the secondary gpu?

I think your psu should be sufficient. 

do you have a dummy plug in the secondary gpu?

I think your psu should be sufficient. 

No dummy plug, each gpu connected to a separate monitor. Shouldn't matter under Linux though.

Yep, I'd have thought the 850 watt would have been plenty, but on the off chance it isn't  I've ordered a cheapish 450 watt psu just to power the card. I'll post results.

Thanks for trying, anyway.

[computerparts]

The BSOD sounds like a driver problem. Try uninstalling drivers with one card in. Make sure you use driver sweeper after uninstall. Then re-install drivers with both cards in.

[Jack of Diamonds]

You said you didn't OC, but did you touch the memory?
 I had that happen on a 4x 5830 rig because 1 card didn't like the memory being underclocked.

Bumping it back up to stock fixed the issue.
At lower memory clocks the system would artifact and lock up instantly after starting a miner.

[sead]

Hi there - I have a 6990 and a 5970 running on a asrock extreme4 - i have 1000W power
- 900W reserved for PCIe. I don't have a power problem - but a cooling problem - i had
to use two PCIe slots (for 2 dual cards - double size) "next to each other" - and there is
not even 1 cm space between the cards. it was not possible for me to use the 5970 in
the possible "third" (4x) PCIe slot (card did not work - or was dead slow)...

I tought like the 6990 running at 880mhz cosumes about 400W (?) in the "normal"
830 mode is should be less than 350W. I am not sure about the 5990 maybe also
350W max.

It of course also depends on other hardware like harddisk and cdrom drives uses
your power...

Good luck

[sead]

please also check your mainboard manual - if the pcie speed changes if there are multible cards used or if its supported at all

[organofcorti]

OK - all sorted now, thanks to drgr33n and computerparts!

For anyone who has similar problems:

Windows - needed to reinstall drivers and clean up old ones.
Linux - had to modify xorg.conf. See post: http://forum.bitcoin.org/index.php?topic=7374.msg307192#msg307192


Also thanks to everyone who responded with good advice.