I'm new on this topic and the last answer is quite old but i had exactly the same problem and i resolved it just yesterday so i think about share my experience and join the forum just for this.
I have :
-2 ATI radeon HD 6950 in crossfire with bridge on a Asus P8P67 revB3 motherboard.
For a long time i was stuck with 13.9 drivers version of CCC because the crossfire worked only ont his version.
I mean worked by the presence of this "ATI CrossfireX" option in the CCC.
Every time i tried to update my drivers even the last 14.4 the "ATI CrossfireX" option disappear from the CCC.
So i read all of this topic and when you start talking about how crossfire worked and how the speed of the bus could interfere in the crossfire, te light come to me....
Indeed, on my motherboard, i have to PCIe slots :
- 1 PCIe 2.0 x16
- 1 PCIe (black) 2.0 x4
So when i put my second graphic card on the black slot, i didnt check anything, just if my motherboard was compatible with crossfire and she is and the crossfire was enabled in CCC with 13.3 version but cant update.
But when you start talking about bus speed i wanna check my slots and i download GPU-Z to check :
- The first PCIe 2.0 x16 was ok and display in GPU-Z with "x16" => good start
- The second (black) PCIe 2.0 worked and GPU-Z display enabled for crossfire BUT the slot was display with "x1" => not good.
SO with recent version, the crossfire CAN'T worked with x16 and x1 slots !!!
So i went to the UEFI Bios of my motherboard and check the black PCIe 2.0 slot and i was configure in x1. So i changed it from x1 to x4 !!!
GPU-Z display crossfire ok with x16 and NOW x4 PCIe slots.
Then i remove all my drivers and CCC components from my computer, restart and try to install the lastest 14.4 version and it WORKS !!
In the CCC, the crossfire option is here and enabled and GPU-Z display also crossfire enabled with x16 and x4 slots.
In conclusion, my advice is :
- Crossfire can't works with x16 and x1
- Check your second slot and turn it from x1 to x4 in your UEFI Bios
- Uninstall proprerly your current driver
- Install the lastest
Hope I help someone. Sorry for my english i'm a french contributor.