when i had my 4850 in the Second Slot the result was the Card not getting enough power (Fan not spinning 100%/5 Blinking Lights). i don't think my Mobo supports this due to the SLI/CF Switch Card. thankfully it didn't damage the Card at all i had the Switch Card flipped to 8x (which wouldn't matter/make any difference to what i was trying). to get a good idea what Mobo needs to Crossfire -A PSU with ATLEAST 500W for the 4Pin Molex Connector found right above the Primary PCI-E Slot -Switch Card needs to be switched to 8x Mode to work in Crossfire Mode that's basically it. the Watts my PSU outputs on the 12V Rails is only 480W (This is my main Concern here!!!) the Rails aren't giving the Volts to power my second Card. this really sucks me having to buy another PSU when i bought this 600W in Dec.!