I just bought a BFG 7900 GT OC with 256MB PCI-E.
I installed it into my system:
AMD 64 3200+ OC'D to 2200 MHZ
1 GIG OCZ Ram DDR
100GB SATA Maxtor
Soundblaster Audigy 2
CASE: Antec TX1050B with True Power 500W at max 35Amps, my voltages are ok at all times I could test it.
So....i installed the card...plugged in 2 molex connectors to the card...and plugged the power supply back, turned on th PSU...and pressed power...nothing.
So... I tried the card without the molex connectors...no power...I tried it with my old video card (Asus EN6600) no power...hmmm did I fry my motherboard?
So...I tried to connect the BFG molexes to a new line straight to the PSU...nothing...
I tried to disconnect and reconnect all powered items...no power...
I tried to disconnect all my fans (not the CPU) and...the system "BURPED" into life...on, off, on, off...I could hear the BFG's fan turning on and off etc. etc. like a turbine trying to start.
After lots and lots of problems and tech support from BFG (they were real nice), I saw some real real strange bnehaviours.
i) The PC rebooted if I tried to enter the bios, many times.
ii)The PC booted into windows just fine without the fans.
iii)If i tried to add a fan (out of my 5 extra fans) and any that I add, the system does not run.
I want to know why my PC witha 500W PSU will not support a BFG 7900GT OC, and a single extra fan...WHY!?
Maybe something is shorting it out. Start over with the motherboard out of the case and sitting on a table/box. Only connect the ram, video, keyboard, power supply. Once you have it posting then connect the rest (one at a time). If not then the problem is within those first items. Try swapping parts if thats available and listen to beep codes. Reseat everything, even the CPU. Your PS is certainly enough. Hope this helps.
I just had a good friend who had the same exact problem. He had the same behavior from the 470MHz XFX 7900GT as you did with the 475MHz BFG 7900GT.
And I do mean exactly, even down to when he tried his previously good 6600GT back in the machine.
I knew he would figure out the problem, and he did. If you have at some previous time, set the cell configuration of your motherboard to the setting which allows for overclocking of the board and all of its components, then you are probably looking at the same problem he had. I refer here to a setting which automatically allows the board to be overclocked to its maximum state.
I can put you in touch with him if you contact me. Thanks and good luck.
Thank you all for your tips.
I will start to investigate this immediately.
However...as luck would have it my temperatures without all the big fans are good....
CPU is about 45 degrees celcius...MB is around 40, and GPU is idle at 66 degrees.
Once I got the system to run without any case fans, my temperatures were still ok ( i have a full tower case).
I ran some games (doom 3, Sin Episodes), and they played great....hmmm.
I decided to add just one small fan on to a cable that is only powering my hard drives.... EUREKA it is alive!.
I tried another fan to the same line....yay!!! I now have 3 extra fans running (out of 5) and my voltages are still the same!!! and my MB and CPU temperatures dropped 10 degrees (C), and my GPU temp dropped 16 degrees!!!!! HOLY MOLY!