Intel and Microsoft spent quite a lot of time on implementing Hyper-Threading technology support in the Windows XP operating system. It has not eliminated possible bugs of the implementation, though. Last year there were a number of cases when the Hyper-Threading technology caused performance decrease rather than increase, and now Microsoft confirms there was in error in Hyper-Threading support by Windows XP SP1 Professional and Home Edition.

As Warp2Search web-site found out, a program that uses large mapped file views to share information between two processes may experience a significant performance decrease. The performance degradation occurs in the UnmapViewOfFile function. Problem occurs if you install Windows XP Service Pack 1 (SP1) on an Intel Pentium 4-based computer that has more than one logical processor (e.g. your CPU supports Hyper-Threading).

A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem. This fix may receive additional testing. Therefore, if you are not severely affected by this problem, Microsoft recommends that you wait for the next Windows XP service pack that contains this fix. Visit this page over Microsoft’s web-site for more information on the matter.

We have seen quite a significant performance increase in various applications when the Hyper-Threading was enabled, though, there are some applications which may suffer from performance loss. It does not mean you should avoid processors with Hyper-Threading, but it means you should try to make sure your software benefits from the Hyper-Threading. Even if Microsoft was unable to implement the technology in appropriate way, no one can guarantee that some other software makers will not make the same mistake.