My Sapphire HD 6870 will not be detected by my motherboard (AsRock Z77 Extreme4) and when I hook it up to a monitor I get no video. I thought it was the motherboard because it is new and the GPU isn't. My old mobo broke so I've been storing the GPU in a box in my room for the past few weeks. But today I tried using a really old really crappy GPU that my brother left here and it worked, video was showing and when I look in my BIOS system map it shows that there is something in the PCI slot (it showed up as "empty" when my 6870 was in the slot). I have confirmed that both PCI slots are functional so there must be something wrong with my card. Should I get a replacement through Sapphire's RMA (I've had the card for more than 30 days so I can't RMA it to newegg). Also does anyone have experience with Sapphire's replacement policy?
I have that same motherboard and I had the same problem with a Gigabyte 6770. My card would work fine on another board but for some reason it would not work on the Asrock board. The way I finally fixed the issue was by defaulting the bios by using the button on the back of the board. After that, everything worked perfectly.
Sorry it did not work for you. I assume your power connection to the Sapphire is working fine. One more thing, I don't remember how I had it exactly but I might have had the VGA cable connected to the onboard when I did this, and I was using BIOS v1.2. From what I've experienced with this board I am not convinced your video card is dead. It frustrated me for awhile too.
I don't mind RMAing my current GPU for a new one. If that one doesn't work then I'm sure that it's not the GPU and I can do whatever I need to do to make it work (although I've tried and tried and nothing seems to work). I don't mind waiting anyway, I've been without a computer for 3 weeks now so at least I can use my PC. In the mean time I'll play some older games.