The hotfix enables Bulldozer to use Simultaneous Multithreading (SMT). This article introduces an update that optimizes the performance of AMD Bulldozer CPUs that are used by Windows 7-based or Windows Server 2008 R2-based computers. Currently, the performance of AMD Bulldozer CPUs is slower than expected. This behavior occurs because the threading logic in Windows 7 and in Windows Server 2008 R2 is not optimized to use the Simultaneous Multithreading (SMT) scheduling feature. This feature was introduced in the Bulldozer family of AMD CPUs. Note This issue may occur when you use applications that run in multiple threads.

KB2645594 (Download here) (install this first) The CPU scheduling techniques that are used by Windows 7 and Windows Server 2008 R2 are not optimized for the AMD Bulldozer module architecture. Therefore, multithreaded workloads may not be optimally distributed on computers that have one of these processors installed in a lightly-threaded environment. This may result in decreased system performance for some applications. When this update is installed, the scheduler will be aware that your Bulldozer processor contains dual-core modules. In essence, threads 1-4 now get assigned to their own module first.

KB2646060 (Download here) (should only be installed after KB2645594) The CPU Power Policies that are used by Windows 7 and Windows Server 2008 R2 are not optimized for the dual core AMD Bulldozer module architecture. This can result in decreased system performance with multithreaded workloads in lightly-threaded environments. When this update is installed, Bulldozer modules will be less likely to achieve the C6 power state. This potentially results in increased power consumption in more lightly-threaded environments.