Graphics card not detected in BIOS or atall?

Hey, well my problem is just as the name of the thread is. I'm running a PCS+ AX7970 on a Gigabyte z77 UD5H with a 3570K. Nothing shows up on the screen when plugged in through the 7970. It dosent even post, it just boots and uses integrated. I've gone through THREE motherboards with this card and none of them work with it. ASrock extreme 6, and ASUS p8z77-v. I would think the card is DOA... but the thing is it worked on one of my friend's computers with an old i7-920. It's completely mind-boggling... twice. I thought it may have been a fluke but it runs rock solid on his rig. I've reset the CMOS about 600 times, turned of the integrated gpu, and ran the pci slot in gen 1, 2, and 3; none of that worked. I updated the BIOS on all the boards and I even used my friends 8-pin connectors for my GPU thinking the power supply would be the problem. Would it matter if I was using my PSU for everything else and his PSU for the card ? intel graphics works just fine, it's what I used to mess around with the bios. The system runs fine otherwise. I have a zalman 850W and it juiced a 4870x2 and another 7970 which I got rid of due to insane coil whine, so I kinda ruled that out but it may be an issue... Oh and on the asus board it worked for two boots after I messed with the bios and psu cables, then it just stopped working again as I reset the cmos because the BIOS was a mess from me playing around with it. Drivers wont install atall and windows dosent detect it as an uninstalled something or other. Any ideas? Thanks in advance!