Problem with 3 6990s

[nimblerobot]

Hi guys, I bought the rig with 3 6990s listed here: https://en.bitcoin.it/wiki/Mining_rig

I've been able to get it set up with any two of the cards with all 4 gpus mining fine but as soon as I power up the 3rd card the system hangs on reboot.

Anyone have a similar experience and have any idea how to get the third card running.

[nimblerobot]

Also, running ubuntu with poclbm

[Departure]

I just bought the same rig lol different Mother board and CPU tho' waiting on a final quote from the Pc shop.. If you do manage to get the 3rd card working can please post the solution in case I run into the same trouble?

[zdmas]

The 6990 is a power hog, you're probably lacking a good and high watt PSU.

[dinker]

lol i think you need atleast 2 PSUs for this rig, even a 1200W will be hard stressed depending on its rail distrubutions.

[Departure]

how much wattage per hour or per day do you think such a rig would consume?

Im trying to calculate of it worth going ahead with the quote and spending the $3000 to get 2000 MH/s and what the electricity would cost

Im guessing it should earn a little over 3 Bitcoins a day I haven't factored in the electricity yet but im hoping to make enough in around 6 weeks to pay off the rig...

[Wynand]

An AX1200W sometimes works on 3x6990. We've had units where it didn't work and where we just added a second PSU.
Don't know the rest of your setup, but it won't pull an intel i7 setup, also, get rid of everything you don't need (2GB ram is just fine), replace that HDD with a flash drive or SSD,..