Microsoft has quietly fixed a problem with Windows XP that disables the power management functions of AMD's line of mobile processors.
The fix allows users of laptops based on Athlon 4 and Duron mobile chips to use PowerNow technology, which extends battery life by reducing processor power when it isn't needed by applications.
The glitch affects people who upgrade the AMD-based notebooks to Windows XP from an earlier version of Windows. The version of XP available on retail shelves doesn't include a driver--amdk7.sys--needed for PowerNow to function, although the driver is included with new laptops using the AMD chips and running Windows XP, according to AMD.
The driver posted on Microsoft's site is dated from late October, only days before Microsoft released Windows XP to stores.
Microsoft earlier this month posted a fix for a Windows XP glitch that caused certain laptops running on Intel's Pentium III processor to freeze.
The AMD incompatibility has not been widely publicized, however, and may be a blow for AMD, which has promoted its mobile chips as having "outstanding performance with Windows XP".
AMD product manager Dave Everitt acknowledged the problem will be an inconvenience to customers but said installing the driver is "a very easy upgrade".
A statement on Microsoft's support Web site reads: "Windows XP Home Edition and Windows XP Professional do not have the ability to take advantage of the AMD PowerNow functionality. Therefore, laptop computers with the AMD Athlon 4 processor do not have the improved battery performance that is offered by the PowerNow technology."
However, manual installation of the driver involves editing the registry, which can disable the operating system if done improperly, so Microsoft doesn't advise it. "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," says a statement on the support site. Microsoft hasn't yet released a service pack containing the fix.
Staff writer Matthew Broersma reported from London.