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Old 11-28-2005, 11:26 PM   #1 (permalink)
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Default Processor Affinity

i'm running windows XP pro.. and when i go into the task manager and right click a process and go down to set affinity...it has the option to run the process on cpu 1 or 2....btw i'm running P4 3.0ht ......so if i set say BF2 to only run on processor 2 would i see a profomance gain? or what is that all about? ( all processes are set to run on both 1 and 2 by default)....thanks for the help
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Old 11-29-2005, 05:13 AM   #2 (permalink)
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The kernel scheduler should balance the load between the virtual processors anyway. A processor with hyper-threading will present itself to the OS as 2 virtual processors. This means that the processor can execute 2 threads simultaneously.
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Old 11-29-2005, 08:43 AM   #3 (permalink)
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but the program usually has to be made so that it will use both "cores" for it to gain an advantage.
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Old 11-29-2005, 10:05 AM   #4 (permalink)
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i see... so a single thread program is useless on a dual core or HT CPU...so untill a dual thread inviroment is around then it's not a real big deal
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Old 11-29-2005, 10:13 AM   #5 (permalink)
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some programs do utilize 2 cores. games are not among them.... yet.
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Old 11-29-2005, 11:04 AM   #6 (permalink)
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Running games on Dual core P4's may actually run slower!!!


From Microsoft:
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.

Possible decrease in performance during demand-based switching
Demand-Based Switching (DBS) is the use of ACPI processor performance states (dynamic voltage and frequency scaling) in response to system workloads. Windows XP processor power management implements DBS by using the adaptive processor throttling policy. This policy dynamically and automatically adjusts the processor’s current performance state in response to system CPU use without user intervention.

When single-threaded workloads run on multiprocessor systems that include dual-core configurations, the workloads may migrate across available CPU cores. This behavior is a natural artifact of how Windows schedules work across available CPU resources. However, on systems that have processor performance states that run with the adaptive processor throttling policy, this thread migration may cause the Windows kernel power manager to incorrectly calculate the optimal target performance state for the processor. This behavior occurs because an individual processor core, logical or physical, may appear to be less busy than the whole processor package actually is. On performance benchmarks that use single-threaded workloads, you may see this artifact in decreased performance results or in a high degree of variance between successive runs of identical benchmark tests.
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Old 11-29-2005, 05:16 PM   #7 (permalink)
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Quote:
Originally posted by apokalipse
some programs do utilize 2 cores. games are not among them.... yet.
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