7900GT Running without PCIE power?

dme92189

Senior member
Dec 26, 2005
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So...I get my new 7900GT, plug it in, and use a converter cable to convert two molex 4 pins into one pcie 6 Pin to power my gpu, but every time i try to start my comp up, it powers on for a split second and dies. Now I am using a DFI SLI-DR board and a 550W enermax psu. Then i tried running the system without pluggin in the 6 pin power connector and it runs and is running games stable... DFI boards have you plug in the 24 pin atx conn, the 4 pin 12v conn, and then also a 4 pin moles and floppy power conn into the board, so what I need to know is if the system is runnign stable without the 6 pin power, is that ok? The gpu is getting adequate power? Thanks guys!
 

996GT2

Diamond Member
Jun 23, 2005
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That is really strange. I know the 7600GT cards don't need a 6 pin PCIe adaptor b/c they can draw all their power from the PCIe slot. SInce the 7900GT is built on similar architecture (more pipelines and lower clocks), maybe it too doesn't draw quite enough power to need the 6 pin?
 

dme92189

Senior member
Dec 26, 2005
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Ok, sure. But then why does my system not power up (fans spin for a split second and then stop) when I have the plug connected for the 6 pin? Thanks for the help btw!
 

996GT2

Diamond Member
Jun 23, 2005
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I had that issue for a while, but not related to the GPU 6 pin. Try resetting your PSU by turning it on and off. If that doesn't work try a different power cable and plug it into a different socket in the wall. Also check the 6 Pin cable for damage. Other than that, I don't know what to tell you.
 

Golgatha

Lifer
Jul 18, 2003
12,392
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Are the two 4-pin connectors on the same length of wire? If so, try using two 4pin molexes on separate lengths of wire.
 

Powermoloch

Lifer
Jul 5, 2005
10,084
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Try power up with just only the bare settings...Mobo, CPU, ram and vid card...and report back to see what happened.
 

gobucks

Golden Member
Oct 22, 2004
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yeah, the 7900GT definitely requires an external power source. when i forgot to plug mine in, it yelled at me in windows and i think it turned down the frequency or something as a safeguard. i plugged it in using the molex-to-pcie adapter though and it worked fine. since the molex adapter requires 2 molex for one pcie, maybe you should try hooking each molex plug up to a different power supply cable. it's possible that a single cable can't supply enough juice.
 

dme92189

Senior member
Dec 26, 2005
687
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ok, tried different power cables, slots. nothing
The two 4 pin conns are not the same length of wire and I am using plugs that come directly from the psu, not pass throughs or y splitters.
When I tried the power up with the bare settings, still didnt work. The only way the system powers on is if i dont connect the 6 pin pcie conn.
 

dme92189

Senior member
Dec 26, 2005
687
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also different psu cables do not work either.
maybe i have a faulty 6 pin converter? or something else?
 

dme92189

Senior member
Dec 26, 2005
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Hahah! Got it! The power adapter i bought was wiring a wrong wire to the GPU, it was sending a current to a pin that was supposed to be grounded!
 

Crescent13

Diamond Member
Jan 12, 2005
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Originally posted by: dme92189
Hahah! Got it! The power adapter i bought was wiring a wrong wire to the GPU, it was sending a current to a pin that was supposed to be grounded!

:p own3d.

Anyway why did you BUY an adapter, it should come with one...
 

Zap

Elite Member
Oct 13, 1999
22,377
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Originally posted by: dme92189
Hahah! Got it! The power adapter i bought was wiring a wrong wire to the GPU, it was sending a current to a pin that was supposed to be grounded!

Lucky your PSU was intelligent enough to cut out before something blew up.
 

RallyMaster

Diamond Member
Dec 28, 2004
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Originally posted by: gobucks
yeah, the 7900GT definitely requires an external power source. when i forgot to plug mine in, it yelled at me in windows and i think it turned down the frequency or something as a safeguard. i plugged it in using the molex-to-pcie adapter though and it worked fine. since the molex adapter requires 2 molex for one pcie, maybe you should try hooking each molex plug up to a different power supply cable. it's possible that a single cable can't supply enough juice.

my 6800GS yelled at me too. the card does need that power. you would be wise to provide.