I just upgraded from a radeon 4860 to a 6870.
The reason I did was my monitor would not come on anymore with my hdmi cable. I tried a dvi to hdmi but still black screen. When I got the 6870 hooked it up exact same thing. On board VGA works fine with monitor and when I hook monitor up to my laptop via hdmi it comes right on. Any suggestions?
I doubt if you inserted the graphx card in the wrong slot. there are mainly 2 slots of PCI-e, 1X and 16X. If the card is fixed in 1X slot, it wont work. Try fitting it in the same slot that of Ati radeon hd 4860 was inserted in.
Maybe thats the problem ur monitor is not working with this graphics, and working fine with onboard graphics.