Required PSU for a 5850 and a 6870 combined

[bad1990]

I have a seasonic gold 750w psu and from what i understand the 500W is good ennough for a 5850 and the 6870 only needs 150w so my 750 should be good?
I can get both cards to run individually but when I try to boot the secondary card on a powered 1:16 riser nothing happens ans it wont boot and the only conclusion that I cna come to is psu issues

[complang]

750 is more than enough! I'd say you would be fine with 500-600W if you let the CPU "idle" (aka. not mining).
I'm running a Dual CPU Quad core (mining FTC = total 7 active cores), 1x5870 (mining LTC) and 1x6450 (also mining LTC). This under a 600W PSU without any problems.

[bad1990]

Okay well i think im going to shut er down and try to get the dual card setup going again and ill post back with any issues

[bad1990]

still cant get er going, second card just refuses to boot,  i guess the last option is the riser doesnt work but i bought it brand new so i am thinking it has to be something else
because both cards work on idividual boots, both fans run when booted together but only my primary, 6870, will boot with both and i cant switch the setup cause the riser wont fix under the 5850, guess my options would be try a new riser or get a new mobo?

[complang]

Aint you able to try without the riser?