I've recently purchased a 7870 tahiti Le to upgrade from an old HD3870 video card.
However, when I connected the card (using the two 6-pin power connectors), there is no output and the monitor receives no signal. The fans are spinning and there are no beeps from the motherboard. I tried using HDMI and DVI to no avail. Additionally, If I remove one of the 6 pin connectors and leave one in, then I can hear the PC booting up and Windows starting. However, the monitor still does not receive a signal. I tried this with each of the 6-pin connectors to see if power was flowing through (I don't have a multimeter to test volts/amps) and it is the same.
If I put my old card back in (Radeon HD3870), then it works fine.
My question is: Is this an issue with my power supply?
Motherboard: Intel DP45SG
CPU: Quad Q9300
RAM: 6GB PSU: Seasonic S12 500W (the old one, few years old - I believe it was this one: http://www.seasonicusa.com/s12.htm )