This thread was created to serve multiple functions: 1.)Create a “one-stop-shop” for all information/links/support for individuals having issues enabling Crossfire. 2.)Outline the specific steps required to correctly install Crossfire hardware/software. 3.)Provide documented proof that Crossfire does indeed work within Crysis (in XP & Vista). None of these discoveries can be claimed as my own. This is merely a compendium of information that has been widely available for some time. It seems (from the sheer number of people having issues enabling Crossfire) that these discoveries were either ignored as false information or were not implemented correctly by the user. What follows are the steps for receiving those extra frames for which you paid a premium. Ready? Let’s go! Starting with the basics, make sure that your motherboard is Crossfire capable. Check to see if your chipset drivers are up to date. Another consideration is the particular chipset you are running. This will determine the bandwidth (number of lanes) of your PCI-E slots. Common layouts are as follows: 16x + 4x Example chipsets: 690 & 790, P935 & P35 8x + 8x Example chipsets: 480X & 790GX, 975X 16x + 16x Example chipsets: 580X & 790FX, X38 & X48 With the exception of the newest chipsets that provide 16x + 16x PCI-e, it is has been shown that when you pair the latest generation of ATI cards with Intel chipsets that 8x + 8x is preferable to 16x + 4x. Example of 975X vs. P35 with 2900. The disparity in performance appears to grow when you move to the 3800 series. A current version of DirectX never hurts either. *Vista Users: UPDATE* I wanted this thread to be a resource, so I'm adding what seem to be essential Hotfixes for Crossfire. Two are available for download: KB940105-Pertains to Virtual Address space/Memory usages. KB936710-For Multi-GPU scenarios. The third is available only by submitting a "Request Form". KB945149-Addresses how the DMA (Direct Memory Acess) packet schedules work to the LDA (Linked Display Adapter). Plus check and see if you have Performance and Reliability updates KB938194 & KB938979 On to the goods… the first point of reference was the ParkOz . This is my culmination of their findings. (Vista users can replace Steps 7 & 8 with a plain boot and power down. Vista will install the driver on the second card automatically. 1.) Start by removing the drivers first with the ATI Uninstall Utility via the Add/Remove Programs of the Control Panel. 2.) Then uninstall the current Display Adapter(s) via the Device Manager. 3.) Power down and remove second card (if applicable). 4.) Boot into “Safe Mode” and use Driver Cleaner Pro to remove misc. drivers & registry entries. Follow up by using “Search” in the “All Files and Folders” with “ATI” as the search criteria for “All or part of the file name”. This will help clear any stragglers. 5.) Boot normally and install Catalyst flavor of choice. 6.) Power down and install second card (do not install Crossfire bridge at this point!). 7.) Boot and CANCEL out of Hadware Installation Wizard. 8.) Find second card in Device Manager (the Display Adapter with the yellow triangle) and right-click to “Update driver”. Use specific location and browse to original Catalyst install folder. (Normally C:/ATI/SUPPORT/8. xxxxxxx.xxx/DRIVER/(select folder based on current OS). This should install the driver on second card. 9.) Power down and install Crossfire bridge. 10.) Copy the folder provided at the bottom of this post into your Crysis directory: Electronic Arts>Crytek>Crysis>Game and replace/overwrite everything.(Make a backup of your original, just in case!) It is just the entire "Config" folder from the Crysis SP Demo. Use you own copy if you feel more comfortable. 11.) (Tech)Power up, open Catalyst Control Center to “Enable Crossfire” and ENJOY! 11 easy steps to smooth gaming! Now for the results. All Benches were run at the same settings (High) on a patched retail version of Crysis. Crysis Hotfix drivers in XP and Catalyst 8.1 in Vista. Crysis Benchmark Tool by MadBoris. In XP: Single card & Crossfire@ 1280x1024, 1650x1080, 1980x1200 Average increase in XP: 34% @ 1280x1024 41% @ 1650xz1080 50% @ 1920x1200 In Vista: DX9 Single card @ 1280x1024, 1650x1080, 1980x1200 DX10 Single card @ 1280x1024, 1650x1080, 1980x1200 Crossfire in DX10 & DX9@ 1280x1024, 1650x1080, 1980x1200 Average increase in Vista: DX9 46% @ 1280x1024 49% @ 1650x1080 55% @ 1920x1200 DX10 9% @ 1280x1024 6% @ 1650x1080 6% @ 1920x1200 This worked out to an average increase of 41.6% in XP, 50% in Vista (DX9) and 7% (DX10)! What surprised me the most was the actual improvement in Vista DX9! There was an annoying amount of flickering in both DX9 and DX10 when running the benchmark in Vista that was attributed to Catalyst A.I.. Apparently the A.I. Is not very adept a approximating textures and LODs within Crysis. The good news is that, contrary to popular belief, I was able to disable Catalyst A.I. when running Vista and Crossfire still worked (and looked great to boot.) There is a performance hit that comes with this change. So when I hear that Crossfire doesn’t work in Crysis (Vista), in part they are right but there is no "magic" involed to get it up and running. It does seem that the DX10 path gives Crossfire the fits, but part of me wonders if it isn’t a DX10/ATI thing instead of a Crysis issue. The question has been raised about the 3870X2, my thought is that since the Crossfire is always enabled, this will not be solvable by the end-user. So everyone should band together and demand that ATI get Crossfire to work correctly! Now, go get your Crossfire on!