AMD processors based on the company's Bulldozer design have gotten hammered by tech reviewers for lower performance than expected on PCs. A few days ago, Microsoft actually released a hotfix that in theory would have boosted the performance of Windows 7 on PCs that have the Bulldozer processors.
VR-Zone reports that at the moment, Windows 7 sees the Bulldozer chip as a quad-core processor but with eight threads, rather than an eight core processor which is, of course, how the chip was designed by AMD. The hotfix was designed to improve the scheduling for threads on Bulldozer chips and would have boosted performance by two to seven percent.
However, Microsoft pulled the hotfix for Windows 7 soon after it was released. Early reports indicated that there was actually a performance drop when the hotfix was installed. In a note on the download web page Microsoft states:
AMD and Microsoft are continually working to improve hardware and software for our shared customers. As part of our joint work to optimize the performance of “Bulldozer” architecture-based AMD processors we collaborating on a scheduler update to the Windows 7 code-base. The code associated with this KB is incomplete and should not be used.
There's no word on when the Bulldozer hotfix will be re-released.