A couple months ago I purchased a Asus M4A78T-E AM3 AMD 790GX HDMI ATX Motherboard. It has a AMD Phenom II X4 955 Black Edition 3.2 GHz Quad Core Process with 3GB of Patriot Viper DDR3 SDRAM 1333 (PC3 10666). Driven by an Ultra 1000w PSU. I recently updated my BIOS to v2303 from the initial version available on the installation CD. Three weeks ago I purchased two Sapphire Vapor-X (100284VXL) Radeon HD 5750 1GB 128Bit GDDR5 PCE I Express 2.0 X16 HDCP Ready CrossFireX Video Cards.
After follow the instructions provided and installing the two video cards neither of my monitors came on. The instructions are not clear about the installation of the CrossFire bridges (interconnect). Should I use one or both. Logically, both would be my answer.
I did get one card to work which is how my system is configured now. I still can not get the second video card to work. I think the problem lies in the BIOS configuration, yet the instruction are not too clear. I do not want to cause something to fail. BIOS information that I have is this. The Mobo and video card are installed in their default values, not overclocking.
PCI Express Configuration (I don't know what this means below)
Port #02 Features
Gen2 High Speed Mode [Auto]
Link ASPM [Disabled]
Link Width [Auto]
Slot Power limit, w 
Port #03 Features
(Same as above)
Port #04 Features
Port #05 Features
Port #06 Features
Port #07 Features
NB-SB Port Features
Yes, I uninstalled my GS 8800 driver and removed it from the device manager. Shutdown removed card, installed both cards and one bridge, standard boot up to windows 7, installed driver, Cat Cont Center indicated Crossfirex active, device manager showed both cards. Started up MWR both monitors went black but the PC kept running. Preformed hard shutdown and began troubleshooting.
I thing the BIOS is not leting configure the second PCI-E slot to x8. There just is not enough information available to understand the BIOS and how to configure properly.... Frustrated