Having moved per AW Tech suggestion my 2nd ATI 5970 from slot 3 to slot 5 to reduce heat - and AW having installed replacement cards for other reasons - (they messed up when trying to install a different driver - I also used a Aug 6 Acronis Image of the C: Drive partition to fix the software mess) - I checked to-day via the Catalyst Control Centre whether the replacement cards had the latest ATI Bios version - they do.  However I noted while the first 2 GPU show

Graphic Bus Capability PCI Express 2.0

Maximum Bus Setting PCI Express 2.0x16

For the 3rd GPU there is no such information

For the 4th GPU it shows

Graphic Baus Capabilty PCI Express 2.0

Maximum Bus Setting PCI Express 2.0x8.

Based on the Technical Manual PCI Slots 1, 3 and 5 are listed as 2.0x16 for my AW Area 51 ALX. For full system specs see my profile

NOTE: Based on an older CCC printout when cards were in slot 1 and 3 and using Driver 8.762 (now using 8.872)  all FOUR were listed as x16.  (System Bios in both cases A10.) 

Do I need to make appropriate changes in that BIOS for slot 5 so that those tow GPU's also show x16?  or is there perhaps a problem with the latest ATI driver/CCC?