My computer stopped detecting my graphics card.

[Gern]

I woke my computer up a couple days ago, and nothing was being displayed on my screen. So I hard-restarted the computer, only for it to be he same. I then unplugged my HDMI cable from my graphics card port, and [plugged it into the motherboard's HDMI port, and the screen came on. The computer had booted to the desktop graphics card and was no longer detecting my AMD graphics card. I shut down my computer, removed my graphics card blew everything out and cleaned it all really good, then plugged it back in and rebooted the computer, but nothing had changed. No matter how many times I scan for changes in hardware in the device manager, it never detects my AMD XFX R7700 graphics card, and I've looked under every section, not just the display drivers section. I am aware that sometimes it can show up with a different name, but I have not seen any devices that it could be. I did a clean install of windows, and it's still the same. I uninstalled all my AMD drivers and tried to reinstall them, but they wont install because it wont detect any AMD hardware. What can I do to make my computer detect my graphics card?
 
I have windows 10 64bit, and everything is up to date. My graphics card, and everything else has been working fine with windows 10 for several months, until now.
 
I took an old geforce 430 out of my old computer and put it in, and the computer detected it just fine. So it's not the graphics card port or anything. My computer still will not detect my AMD XFX R7700 graphics card.

[DaveLembke]

Its quite possible that the chip that identifies the card in the PCI bus is blown on the card and so power and data/address lines are connected but no answer at the door and the system just walks on by after no answer to the next device as if its not there.

If the video card is still under warranty i'd get it replaced for free, otherwise your looking at getting a new videocard or running the Geforce 430.

*There is a very slim chance its related to power supply weakening.... but I feel its the card. If you have a known good power supply you can swap it out and see. I assume the 12V molex is connected, however the 12v could be too weak and cause this meanwhile the 430 is likely only powered through the PCI Express slot with molex not needed and thats why it runs. If the 12v is weak it should be also affecting hard drive etc unless your running SSD thats powered only from 5V etc.

[Gern]

Well, even the old geforce 430 doesn't really work either. It works fine for about 20 minutes or so, then goes out just like the AMD. However, unlike the AMD, which my computer will not detect ever anymore, the geforce will still be detected by my computer and work fine after I restart my computer. At least it does for another 20 minutes or so. This only started today. I ran my computer for several hours last night using the old geforce 430 graphics card, and it did fine. Any idea what that could mean?

[patio]

Is there another video slot available ? ?...if so remove all power and swap the card into it...

[DaveLembke]

hmmmm .... if you have a spare good power supply swap out power supply... system warms up and the voltage drops is what Im thinking on the 12V side