I'm trying to install a pair of new ATI Radeon HD 4890 graphics cards into my ASUS P5W DH Deluxe motherboard, but when I install them, the computer won't boot. No BIOS: nothing but whirring fans that won't quit or slow down.

I tried using just one of the cards, WITHOUT the CrossFireX system, but that changed nothing.
I had to put my old (malfunctioning) cards back in just to turn the computer on.

Does anybody have any idea what's wrong or how to fix this?Install 1 at a time...load the drivers and re-boot.
Then follow the instructions from the board manuf. on setting up a crossfire setup...I can't install either one if the computer won't START.Remove both of them and start over...1) What's the WATTAGE of the power supply you're using? 2 x 4890s in Crossfire is going to require some juice...

2) Do you have the six-pin PCI-e connectors from your power supply plugged into both cards?I managed to resolve the issue.

It TURNS out that each card has two 6-pin PCI-e connector ports, and each requires power from both at the same time, meaning I needed four PCI-e 6-pin power connectors for both cards.

My power supply only has one cord that splits into a pair of the plugs, which was fine for my old cards, but only half of what the new cards needed. Luckily, the new cards each came with a pair of 4x1-pin to 3x2-pin (PCI-e) adapters, and I was able to use this to fill in the missing power requirements. Booted right up after that.

Surprisingly, there is absolutely no hint in the installation instructions that each card requires a pair of power cords. I guess the manufacturer just assumed I would automatically know that they doubled the necessary connectors to the new cards. I was expecting the new cards to be LIKE all the other cards I've played with...

Meh. PICNIC and cheap instructions. Thanks for the effort everyone. Hey Hunter484 - How's performance with these cards in crossfire configuration with the Asus P5W MB? I'm thinking of doing the same soon. Cheers, Chris.