# Solved: Motherboard will not detect graphics cards



## Santana (Sep 23, 2007)

So, I had a power outage and my PC wouldn't start up afterward. I took it to a computer repair shop and they determined it was the motherboard. I replaced the motherboard now, installed Windows 7 again (but kept the old files on the HDD, as custom install lets you do, it just partitions the drive), and only the on board graphics is working. I can't get my PC to detect any graphics card despite plugging them into the PCIe x16 slot (closest to the CPU) and their fans coming on. There is no indication of a graphics card in Device Manager.
Things I have tried:
-Updating BIOS
-Installing most recent chipset drivers
-two different graphics cards (560 Ti and 6850)
-updating Windows, including all optional updates
-Going into the BIOS, selecting primary display as PEG (which is the PCIe slot), it saves, I plug in a monitor to my GPU, nothing, but I plug the monitor into the on-board graphics and it works. The option for primary display is reset in the BIOS back to "Auto select" after this.
-Tried the PCIe x4 slot, it doesn't detect them
-I tried installing Nvidia/ATI drivers, but they won't even install because I don't have the proper hardware (card not detected)

I'm not sure what to do now... I don't think the slots are dead because neither PCIe slot works. Am I missing some sort of motherboard software or is it a compatibility issue? I'm really at a loss here.

Specs:
Windows 7
4 GB DDR3 RAM
Motherboard: Gigabyte GA-B75M-D3H
PSU: Corsair GS600
CPU: i5-2500k
GPUs: EVGA GTX 560 Ti and MSI Radeon 6850

EDIT: I haven't tried disabling on-board graphics yet (just made sure PCIe was the priority), because if that doesn't fix it, then I won't have any display and will have to reset the mobo (last resort).


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## managed (May 24, 2003)

I think you should bite the bullet and clear the Bios/Cmos to see if that helps.


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## dustyjay (Jan 24, 2003)

It is possible that the same thing that killed the motherboard may have also killed the video cards


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## saikee (Jun 11, 2004)

Have you tried to disable the onboard graphic facility?


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## Santana (Sep 23, 2007)

dustyjay said:


> It is possible that the same thing that killed the motherboard may have also killed the video cards


No, not possible.



saikee said:


> Have you tried to disable the onboard graphic facility?


Well, I mentioned that in the edit. It's a last option because then I might end up with no display.


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## saikee (Jun 11, 2004)

Others may give a better explanation but I believe the mobo can only drive a one set of graphic display at a time. Multiple displays arer possible within one graphic card if it has that function as most expensive cards got it. If an onboard graphic and a plug in graphic card are offered to a mobo it must make a decision to send the signal to one device.


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## Santana (Sep 23, 2007)

saikee said:


> Others may give a better explanation but I believe the mobo can only drive a one set of graphic display at a time. Multiple displays arer possible within one graphic card if it has that function as most expensive cards got it. If an onboard graphic and a plug in graphic card are offered to a mobo it must make a decision to send the signal to one device.


I guess I can give it a shot. I've never cleared a CMOS before, but it seems easy enough and I'm really out of options.

Shouldn't the GPU at least show up in Device Manager, though, even with on-board going?


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## saikee (Jun 11, 2004)

Santana said:


> Shouldn't the GPU at least show up in Device Manager, though, even with on-board going?


That I don't know.

However if the mobo cannot send graphic signal to every graphic card plugged in by a user and must decide to send the signal to only one device then the Device Manager should not report the unused hardware because the BIOS would not hand that information to the OS.

If you see the device in the Device Manager that means you should be able to use it.

Multiple displays are embedded function of a good quality graphic card that can handle and configure the monitors plugged to it. That is based one one signal source.

I just don't think a mobo is ready or clever enough to manage one grahic signal for two different hardware because the combinations (screen definition, vertical frerquency, horizontal frequency, colour etc) could be impossible to cope but I could be wrong. The minimum function of any multiple display is the display can be a repeat of each other or an extention of the other.

I have several mobo that have onboard graphic but I always added a better one in each. I think modern mobo can sense the port and select it for display. Thus your question should be if a mobo has selected one graphic card device to communicate with a user could it still make use of another grahic device ?

This web page suggests the onboard graphic card should be disabled in the Device Manager.


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## closetvibes (Nov 30, 2014)

http://www.gigabyte.com.au/products/product-page.aspx?pid=4150#manual read the manual - you have 2-way CrossFireX™ multi-GPU support everything you need to know is in that manual --- ( print out the page you want so it is available offline when you need it )


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## Santana (Sep 23, 2007)

I've read the motherboard manual, but I didn't see anything in there that would solve this.

Anyway, I went ahead and disabled the integrated graphics in device manager, then disabled them in the BIOS, then I set the primary display to PEG. I connected up my monitor to the card and booted. The POST was a long beep followed by 2 short beeps, which I believe means the motherboard has no display to connect to. So, that solution didn't work.


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## 88tarot88 (Nov 30, 2014)

same power supply as when you ahd the outage?
try swapping that or
grab a pcie power adapter and throw them on a couple of molex plugs and try that.
to me it looks like a power issue


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## Santana (Sep 23, 2007)

Yea, same PSU. The PC works fine otherwise and the fans come on for both GPUs, so could that be a power issue still? I'll try another PSU tomorrow or something.


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## 88tarot88 (Nov 30, 2014)

check the box your video cards came in most come with a molex/pcie splitter.
fans only require X power, the pcie slot will provide some of the power but most bigger video cards needs extra.


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## Santana (Sep 23, 2007)

Turns out both of the graphics cards I was testing were dead!


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