I have been testing with the use of three simlar spec systems all powered by Ati 5870.
2 rigs have 2 5870 in Xfire & 1 rig has a single 5870.
Xfire was tested with and without MSI afteburner locking no1 & 2 cards to give standard clock speeds for both cards on boot for Xfire rigs.
Testing was done with the Black death track from start to where the close up of the soldier on the AA Gun is seen.
fps SHOW LOG command was used so when the track was paused and the consol bought up again there was a good number of AVE MAX & MIN frame logs to be seen.
ON the internet i checked my rig against my Squadies other Xfire rig and found whatever in game video settings used the results were the same on both rigs.
Testing At VHI HI MED & LO in GAME settings
I checked my rig against the
Single 5870 rig and found the results the
same even though I had Xfire running.
Disabeling my second card gave me the same result again.
Double checking with afterburners 2 x temp & 2 x GPU`s chart showed that Both cards worked on Xfire and only one when I disabled Xfire on my rig.
Conclusion
Despite aterburner showing both cards working in XFIRE mode ,and the Xfire icon showing in game it appears it is actualy having no effect in the game (at least for 5870`s ).
Could it be both cards are rendering the same frame instead of alternate frames :ie
Alternate Frame Rendering - Just like with SLI's Alternate Frame Rendering mode, each frame is rendered by each GPU one after the other. For example, the first GPU will render all the even frames while the second GPU will render all the odd frames.
The other Xfire rendering modes are :
Supertiling Mode - Supertiling works by dividing the screen/frame into small squares of pixels and spreading them evenly to each GPU for processing.
Scissor Mode - In scissor mode the frame is split up into two pieces, depending on rendering effort. The two GPUs are given each half of the frame for processing.
Whatever mode is used by Cliffs of Dover it does not appear to be working on 5870 cards .
Hope this info helps someone figure out the problem.
Thanks to Pedro & Brando for use of rigs for testing.
Beta 15866
System Information
OS Name Microsoft Windows 7 64 bit Home Premium
Version 6.1.7601 Service Pack 1 Build 7601
System Type x64-based PC
Water Cooling (CPU & GPU`S)
Gigabyte GA-890FXA-UD5 BIOS Version/Date F6,
24/11/2010
SMBIOS Version 2.4
1000W Corsair PSU
Processor AMD Phenom(tm) II X6 1100T Processor, 3817 Mhz,
RAM 8.00 GB 2x4GB 1600mhz Corsair Dominator
Vertex 240GB SSD Hard drive
1xSeial DVD reader/writer
2xATI Saphire 5870 OC Vapour X
Steel series USB soundcard & Headset
Saitek X52 PRO
2xThrustmaster MFD`s.