PSU requirement for 2 x 6950's?

[Oldminer]

Hi all

Ive picked up another 6950 today but cant get it to mine while the other ones mining also. It starts to hash but then the PC just reboots after a second or so. Im thinking PSU but I have an 800W PSU. The cards are NOT in crossfire and from what I can find it appears the maximum draw from both cards should only be about 470W total? Aside from the cards Im running 2 SSD's and 1 HDD (as well as an optical drive and some case fans). Any ideas? Both cards run fine individually. Ive also done a fresh reinstall of Windows 7.

Also, I noticed this is the AMD control panel:

Primary Adapter      
Graphics Card Manufacturer   Powered by AMD   
Graphics Chipset   AMD Radeon HD 6900 Series    
Device ID   6719   
Vendor   1002   
   
Subsystem ID   03D4   
Subsystem Vendor ID   1043   
   
Graphics Bus Capability   PCI Express 2.0   
Maximum Bus Setting   PCI Express 2.0 x16   
   
BIOS Version   013.010.000.009   
BIOS Part Number   113-AC98400-111   
BIOS Date   2011/01/26   
   
Memory Size   1024 MB   
Memory Type   GDDR5   
   
Core Clock in MHz   810 MHz   
Memory Clock in MHz   1250 MHz   
Total Memory Bandwidth in GByte/s   160.0 GByte/s   
   
   
Enabled Adapter       
Graphics Card Manufacturer   Powered by AMD   
Graphics Chipset   AMD Radeon HD 6900 Series    
Device ID   6719   
Vendor   1002   
   
Subsystem ID   2307   
Subsystem Vendor ID   1787   
   
Graphics Bus Capability   PCI Express 2.0   
Maximum Bus Setting   PCI Express 2.0 x1<--------------------------??
   
BIOS Version   013.010.000.004   
BIOS Part Number   113-C2050100-016   
BIOS Date   2011/01/20   
   
Memory Size   1024 MB   
Memory Type   GDDR5   
   
Core Clock in MHz   800 MHz   
Memory Clock in MHz   1250 MHz   
Total Memory Bandwidth in GByte/s   160.0 GByte/s   

[Oldminer]

Ok I was able to enable the 2nd card in the BIOS to run @ PCI-E 2.0 x 4 (no option to go higher) & can run 2 x miners in Crossfire (which restricts me to using just 1 monitor) but not separately. The second card only runs @ 100 Mhashs/s in this configuration. So it seems my PSU is ok.

But I have 3 monitors in total including my main monitor & Ive got the 2nd card plugged into 2 monitors but it doesnt see them at all (even if not running CF). I can get 1 of these monitors enabled by plugging it in to the same card that the main monitor is plugged into (and extending the desktop) but the 3rd ones not seen at all. If I swap them around it works fine also on the 2nd card so neither the card is faulty. Now I could be wrong here but arent these cards supposed to be able to run 6 monitors all up? Admittedly the 2 smaller side monitors are a few years old now but I have them coupled up to VGA-DVI adaptors and they worked fine on an old cheapy vid card I was using before. I'm thinking I could buy a splitter cable and run the 2 side monitors off the 2nd DVI port on the main card but this still doesnt get me round the fact I cant mine with both cards at the same time (except under CF). Ive seen posts on here about running 'dummy plugs' but isnt that only something you need to do if you only have 1 monitor and doesnt apply to Win 7 anyway? Kinda miffed atm..

[computerparts]

Ok I was able to enable the 2nd card in the BIOS to run @ PCI-E 2.0 x 4 (no option to go higher) & can run 2 x miners in Crossfire (which restricts me to using just 1 monitor) but not separately. The second card only runs @ 100 Mhashs/s in this configuration. So it seems my PSU is ok.

But I have 3 monitors in total including my main monitor & Ive got the 2nd card plugged into 2 monitors but it doesnt see them at all (even if not running CF). I can get 1 of these monitors enabled by plugging it in to the same card that the main monitor is plugged into (and extending the desktop) but the 3rd ones not seen at all. If I swap them around it works fine also on the 2nd card so neither the card is faulty. Now I could be wrong here but arent these cards supposed to be able to run 6 monitors all up? Admittedly the 2 smaller side monitors are a few years old now but I have them coupled up to VGA-DVI adaptors and they worked fine on an old cheapy vid card I was using before. I'm thinking I could buy a splitter cable and run the 2 side monitors off the 2nd DVI port on the main card but this still doesnt get me round the fact I cant mine with both cards at the same time (except under CF). Ive seen posts on here about running 'dummy plugs' but isnt that only something you need to do if you only have 1 monitor and doesnt apply to Win 7 anyway? Kinda miffed atm..

That's only if it has the Eyefinity feature. Not every card is capable. I would only run one monitor and try dummy plugs and see what happens.

[Oldminer]

Thats not really an option. Im going to see if I can pickup a converter and run the 2 small monitors off the display ports rather than the DVI ports.