Outside of its normal update-schedule, AMD has released a hotfix for its Radeon graphics-cards. The Catalyst 10.8b drivers provide some specific fixes and should improve performance of the company's newer GPUs under Windows Vista and Windows 7.
The first fix applies to both the Radeon HD 4870 X2 and HD 4850 X2 and promises significant improvements. Apparently the cards weren't properly using both GPUs, seriously hamstringing performance in certain games. The update should fix that issue, getting the most out of the hardware and putting both cores back to work.
The second change applies to all ATI cards that support DirectX 10 and higher, which includes all members of the HD 3000-, 4000- and 5000-series. Apparently the updated driver will significantly improve performance in Ubisoft's H.A.W.X. when anisotrophic filtering is forced-on through the Catalyst Control Centre. Again, this will only affect users running newer versions of Windows.
Obviously this is just an incremental hotfix, so the list of changes is quite small. Users of AMD's dual-GPU cards should appreciate the improvements, though, as it is expected to deliver a significant performance-boost.
Full details are available from the company's website along with download links for the hotfix.