Problem with Graphics Card(s)

[jasonmwells]

I will try to be brief. My system went out this past week with what I thought was a bad graphics card. Tried 2 replacements cards (new from the store) neither worked so I assumed it was a bad PCI slot on the motherboard. Ordered and installed a new motherboard and new memory, kept the old processor (i7 2600), case, power supply, drives.

Got everything loaded and the onboard graphics (via Intel HD) work fine. I reinstall new graphics card (R9 270) no luck the computer spins up but neither the mouse nor keyboard work and no graphics. Tried old graphics card same thing except the fan on the old card spins really fast. While there is a card in the PCI slot the onboard graphics are disabled. Pull card out of the PCI slot and the onboard works again. So I am stuck don't want to run onboard graphics but can't figure out why machine won't take a graphics card. Only thing I can think it could be at this point is either the power supply or CPU. Can images disk drives causing this issue and everything is new. Any suggestions?

Thanks.

 

[coozie7]

What power supply is installed?
Check the motherboard manual, not all will automatically disable the onboard or automatically activate a dedicated graphics card, my MSI 'board is a late design (Z97, UEFI BIOS) but needs to be told to use the dedicated graphics card for example.

 

[jasonmwells]

The power supply is the stock unit that came with the dell originally in 2011. It is a 450W. I've checked the bios on the motherboard and it is setup so that the PCI Express is the primary with the onboard graphics secondary. The only thing I can think of is that the power supply isn't fully powering the graphics card enough.