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No POST when Gfx card plugged in

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April 15, 2011 12:34:19 PM

Bit of a strange one this.

The motherboard works fine so long as it doesn't have a card plugged into the PCI-E slot. I'm trying to work out whether this is a PSU issue (However a 750W should be more than enough) more than anything but thought I'd feed on others' experience first:

Setup as follows:
M/B - P5G41T-M-LX Proc - Q8300
RAM - Corsair TW3X4G1333C9A
GFX Card - Palit GTS 450 Sonic
PSU - CiT 750UB


Basically what happens is, the system starts up fine as long as the GFX card is not plugged in and I use the onboard graphics. I've tried the 450GTS in another machine with the same mobo and it's fine. What seems to happen when I plug the gfx card in and switch the machine on is that the fans will come on for a second and then go off.

If, after this I remove the card and try to switch on the machine again still get the same problem, fans don't even start up. I have to remove the battery from the motherboard and put it back in before the machine will boot up again. And yes, I've taken all obvious precautions and there is no problem with the graphics card as it works in my other machine (with the same model of motherboard). Anyone else had similar issues? Is this some kind of failsafe that's causing it to not start up

Without the Graphics card in, the machine will boot up into Windows without a problem.

More about : post gfx card plugged

a b V Motherboard
April 15, 2011 12:57:59 PM

TMISv2 said:
Bit of a strange one this.

I've tried the 450GTS in another machine with the same mobo and it's fine. What seems to happen when I plug the gfx card in and switch the machine on is that the fans will come on for a second and then go off.


Thought #1: can you try another graphics card in your PCIe slot? that would be the next logical step. a low power GPU that doesn't require a PCIe cable from the PSU would be the best to try. this would tell you if it was the motherboard or the PSU.

Thought #2: does your psu have more than one 6pin PCIe connector? try posting using the other connector or use the molex to PCIe adapter that comes with your GPU. This will use power from the other 12v rail. If any of this works it would point to a bad 12V rail on your PSU. if it doesn't then your MB is most likely toast.

hope this helps
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April 15, 2011 1:13:40 PM

I've tried another GTS 450 in the board, but that didn't work either (although again it needs the 6 pin connector). I don't have a spare GPU lying around that doesn't have the PCIe cable and as buy one to test it I may as well try out another PSU :) 

The PSU only has the one 6pin connector. I've tried using the molex adapter that came with the card as well and get the same result.

Will pop out and buy another PSU tonight and if that works or not then I guess I'll get my answer one way or the other. If it's the motherboard at least I'll have a shiny new PSU for when I rehome my other rig into the new case I'm planning on getting soon.
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a b V Motherboard
April 15, 2011 3:04:01 PM

if you tried the molex adapter, then I would lean toward a bad PCIe slot on the MB. the PSU could still be bad but the odds lean toward the MB.
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April 15, 2011 11:20:51 PM

Turns out it was a faulty PSU. Bought a decent brand 500W one and it runs like a charm.
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a b V Motherboard
April 16, 2011 12:07:50 PM

Great! goes the prove my point on when everyone tries to skimp on the PSU when building new system. They will blow $300 on a GPU, the try to power it with a $40 PSU. The GTS 450 isn't even a power hungry GPU, yet your off brand PSU had issues.
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