Computer won't POST with 7900GT

[bespoke]

I know lots of people are having trouble with artifacts and lock ups with their eVGA 7900GTs, but I can't even get my computer to POST with the board in. I've been reading/searching forums all over the place, but no one seems to have my problem.

Rig:
eVGA 7900GT KO (replacing X800 XL)
Athlon 64 3500+ Winchester
4x512MB DDR
DFI LanParty UT nF4 Ultra-D
Seasonic S12-430
2 HDs, 2 CD/DVD drives (unplugged for testing, though)

When I power on the PC, the 4 diagnostic/debug lights on the DFI mobo come on. When I have the X800 in, they go off one by one as they should. When I have the 7900GT in, the first light goes off (System start-up) but the second one stays on (CPU detected) and nothing else happens. I don't even get the DFI boot screen.

I should have enough power to run the 7900GT as the Seasonic definitely puts out 430W (or very near) and with no drives plugged in, the mobo, CPU, RAM, and 7900GT should only draw 202W (according to the eXtreme PSU Calculator). As for amps, the Seasonic has two rails, putting out 14A and 15A. Now the 7900GT claims to need 20A to 24A (depending on what source you look at) and while I don't have that amount on one rail, combining the two rails should give me at least 20A.

So, gurus, what do you think? Would marginally less than needed power cause my PC to not boot at all?

I didn't have time to try an older 480W PSU that I have - that will be tonight's attempt. But I got the Seasonic PSU for it's quietness and I'd hate to have to replace it.

 

[Pens1566]

The Seasonic would be my guess. Current on those rails looks a little low for that card. I think the 3rd light on the DFI boards means video card detected. Then again, there is someone over at evga forums that can't boot with his 7900GT installed different MB (MSI) and PSU though. What is your 480W PSU rated at?

 

[bespoke]

Originally posted by: Pens1566
The Seasonic would be my guess. Current on those rails looks a little low for that card. I think the 3rd light on the DFI boards means video card detected. Then again, there is someone over at evga forums that can't boot with his 7900GT installed different MB (MSI) and PSU though. What is your 480W PSU rated at?

I just checked the manual for the LanParty mobo and it says that 3rd light is CPU, so I'm failing to boot from the very start.

480W PSU is a Thermaltake Silent Purepower W0014RU 480W. Newegg lists that as having 18A on the +12v (rig is at home and I'm at work, so while that sounds correct, I cannot verify). Closer to 20A, but still not there. Maybe it will be enough to boot...

 

[Running]

i have heard that seasonic psu's usually have troubles with DFI mobo's

 

[shabby]

Try it in a different comp, as for the psu 430watts is more then enough for a 7900gt.