Does the other rig runs the same motherboard?
I suspect its the motherboard,
LOL at folks who thinks its the PSU. That AX1200 is plenty for this rig. I guess they follow that highly over requirement from ATi.....
I have 4 identical motherboards running various video cards.
2 rigs running 4 6970 (Silver stone stider 1500w PS)
1 rig running 6 5830 (AX1200)
1 rig running 4 5830 & 1 6990 (AX1200)
my inital plan was to to build frames for the systems and then get 7 video cards in each machine
however now that the BC price has dorpped so much... i'm in no hurry to buy more video cards.
but would still 'like' to have as many cards in a single machine
if i can reduce my motherboard count by 1 then it would be some power saved.
You're truly going overboard with PSUs. But i be its good investment and safe setup.
The last rig shows you have plenty of power for 7x 5830s. Its not the power issue, its rather the mobo or crappy extender.
I really think its the mobo. You can remove that 6990 with 2 x 5830s, i bet you would have the same issue.
I think the ceiling is 6 cards. Or you can shuffle the cards around to see if the order of slots matter. I wouldnt spend too much time tho. 6 cards are probably better for cooling and noise.