I just got a new 6870 card, and im not sure if my psu is up to it. 90% of the time when i boot the computer the gpu fan spuns to 100%and the cpu does not display anything on the monitor. If i keep restarting the computer it eventually works...but it is quite frustrating. Psu is a 550w corsair. Any help?
The AMD cards have a feature that throttles power use as per demand. So I do not think it is not enough power at boot (very little or no gpu demand). I would remove the card and check the slot to make sure it is clean and free of and dust or dirt. Then re-seat the card making sure it is in the correct slot (usually the one farthest from the edge of the board). If that does not do it and the system worked with the previous card, you may have a bad card (RMA it).
if i could i would test the card in different PC, if got same result try to exchange it.
from top of my head i would say its BIOS problem, maybe Motherboard+video card compatibility problem
Check and see if you can update BIOS, (reset bios settings maybe as well)