How might I get PCI Express to work on my new/old 939 mobo?


Jan 15, 2012
I can’t get the PCI-E X16 slot to work on my new/old 939 mobo. It’s an old socket 939, but new, right out of the package.

Might be presumptive of me to dump all this info here, but the computer is for my homemade lab and I teach high school in a poor neighborhood, so any help you might give is for a good cause.

Here are the build’s specs:

CPU: Athlon 64 Fx55
Mobo: AN8 VM with Nvidia 6150 onboard, with a pci-e x16 slot
Mem: 2x 1gb sticks of DDR 400
PSU: 600 Watt Corsair

When I tried to install a new pci-e x16 card, Radeon HD 5450, the monitor gets no signal. The computer comes on, does not post (keyboard does not light up), cpu fan and PSU fan both turn on, but nothing else happens.

When I then take the pci-e card out and plug the monitor cord into the onboard video card, everything works fine, but ONLY if I take the pci-e card out. When I leave the pci-e card in and plug the cord into the onboard card there’s still no signal

Things I’ve tried already:

I plugged the card into another computer. It works.

I plugged another pci-e x16 video card, an 8800gt, into this build and the same things happen, no signal.

Tried with both the onboard card’s manufacturer’s driver and the standard window’s driver and tried both of these with them enabled and disabled and uninstalled in device manager

Did most of the trouble shooting here with each of the three latest versions of bios available for my machine.

BIOS settings I tried:

Under Northbridge configuration there are a few seemingly relevant categories of parameters that can be tweaked, “VGA Options” and “Primary Graphics Adapter” are the ones I adjusted, but to no avail.

Under “VGA Options” the choices are ‘Enable’ and ‘Auto’, the descriptions in BIOS of what they do is somewhat muddled.

For ‘Enable’ it says: “enable onboard VGA, this should be chosen only when nvidia external VGA was installed.”

The Auto description states: “disable onboard VGA if external”.

The other parameters of interest, “Primary Graphics Adapter” has two options:

Mostly I troubleshot with “Auto” on and “PCI->PCI-E->IPCIGP” as that seemed to make sense.

Other BIOS parameters that I didn’t try to adjust, but might be relevant are:

OnChip VGA Frame Buffer
OnChip VGA Trap Enable
Under Hypertransport Configuration
LDT to Geforce frequency
Repost video on S3 resume

Then there’s the IRQ stuff, under which there’s an option to “Allocate IRQ to VGA.” I think the choice there is to have BIOS do so automatically.

The mobo is right out of the package and everything else works like a charm. My two 1 gb mem sticks might not match.

Everything is clean and all connections have been checked and double checked, what’s more I’ve tested the cards and monitor and they work.

It must be either the pci-e X16 slot is broken somehow but hopefully I’m missing something in BIOS which someone here can shed some light on. Thanks in advance.



I had a similar problem with a socket 939 motherboard. I replaced the Radeon HD 5450 which was a PCIe 2.0 card with a Radeon HD 4350 which was a PCIe 1.0 card and it worked fine. Apparently, the PCIE 2.0 capable card was not compatible with the PCIe 1.0 slot on the motherboard.

I checked on the 8800 GT on Newegg. Even though all of them were discontinued, I didn't find one that said it was PCIe 1.0 so it's likely that you have the same issue with that card. See if you can find a graphics card that is specifically designed to work in a PCIe 1.0 slot.


Jan 15, 2012
Thanks. Have the latest BIOS. And have a 7600 gs at work, I'll try it with that.

Strange. This is my fifth 939 board and never encountered this problem before.