Microsoft announced a bug in the Vista operating system related to the operation of both GPUs in SLI and Crossfire configurations.
Under Windows Vista-based computers equipped with a high-performance video card with multiple graphics processing units (GPUs), the computer's graphics performance was low indicating that only a single GPU was in use.
The problem occurred because the operating system did not forward driver-render requests to the secondary GPU, according to Microsoft.
Microsoft said that it is currently testing the software patch for the specific issue. A hotfix patch is expected to be included in the company's next service pack. For additional information, visit http://support.microsoft.com/default.aspx/kb/936710/en-us