SYMPTOMS
Computers that are equipped with multiple processors that support processor power management features, such as Advanced Configuration and Power Interface (ACPI) processor performance states, require Microsoft Windows XP Service Pack 2 (SP2). Additional updates are available to optimize performance and behavior on computers that are running Windows XP SP2. Without these updates, computers that are equipped with these power management-capable, mobile, dual-core processors may experience decreased performance or unexpected behavior.
Note This problem also applies to x64-based versions of Microsoft Windows Server 2003. However, this article and its associated private hotfix are not intended to resolve timing problems in games and other applications that run on AMD dual-core computers. For more information about performance issues on dual-core computers, click the following article number to view the article in the Microsoft Knowledge Base:
MORE INFORMATION
Windows XP SP2 is required on computers that have multiple CPUs that support ACPI processor performance states. This requirement includes computers that support the following items:
? Multiple physical sockets
? Multiple-core designs
? Multiple logical threads, such as Intel hyper-threading technology
Because Windows XP was not originally designed to support performance states on multiprocessor configurations, changes are required to correctly realize this support on multiprocessor systems. Windows XP Service Pack 2 includes the required changes to the kernel power manager. These changes make sure that Windows XP correctly functions on multiprocessor systems with processor performance states.
This hotfix also addresses the following issues on computers that have multiple processors that support processor performance states:
? A possible decrease in performance on single-threaded workloads when processor performance states are using demand-based switching.
? The synchronization of the processor Time Stamp Counter (TSC) registers across processors when you use the ACPI Power Management timer on multiprocessor systems.
? ACPI C-state promotion and demotion issues in the kernel power manager.