System Idle Process...my system can wait twice as fast as ..

Archived from groups: microsoft.public.windowsxp.customize (More info?)

Something interesting I just noticed. No biggie, and my observation is open
to interpretation, but I thought it interesting nonetheless...

I have a hyperthreaded Xeon CPU (though I suspect XP would have the same
behavior with any hyperthreaded CPU). In Task Manager, the CPU Time value
for System Idle Process is moving at twice the "real" time rate. That is,
for every second of real time, the CPU Time value increases by two seconds.

I also have a machine with two physical CPUs, each with hyperthreading (thus
4 CPU graphs under the Performance graph). On that machine, System Idle
Process is moving ahead 4 seconds for every second of real time.

I noticed this because my system has been on for rougly 24 hours, yet Task
Manager reports that System Idle Process has been running for 48 hours.

Surely I'm not the first to notice this? Anyone know of some news group or
forum where this has already been discussed?

(if hyperthreading is disabled in the BIOS, then the time advances normally)

Thoughts?
2 answers Last reply
More about system idle process system wait fast
  1. Archived from groups: microsoft.public.windowsxp.customize (More info?)

    With my limited knowledge of hyperthreading, I understand that a
    hyperthreaded processor is seen as two processors and therefore the cpu time
    in task manager is counting both processors simultaneously.

    "Homer J. Simpson" <root@127.0.0.1> wrote in message
    news:Oz$pNnCnEHA.3820@TK2MSFTNGP09.phx.gbl...
    > Something interesting I just noticed. No biggie, and my observation is
    > open to interpretation, but I thought it interesting nonetheless...
    >
    > I have a hyperthreaded Xeon CPU (though I suspect XP would have the same
    > behavior with any hyperthreaded CPU). In Task Manager, the CPU Time value
    > for System Idle Process is moving at twice the "real" time rate. That is,
    > for every second of real time, the CPU Time value increases by two
    > seconds.
    >
    > I also have a machine with two physical CPUs, each with hyperthreading
    > (thus 4 CPU graphs under the Performance graph). On that machine, System
    > Idle Process is moving ahead 4 seconds for every second of real time.
    >
    > I noticed this because my system has been on for rougly 24 hours, yet Task
    > Manager reports that System Idle Process has been running for 48 hours.
    >
    > Surely I'm not the first to notice this? Anyone know of some news group
    > or forum where this has already been discussed?
    >
    > (if hyperthreading is disabled in the BIOS, then the time advances
    > normally)
    >
    > Thoughts?
    >
    >
  2. Archived from groups: microsoft.public.windowsxp.customize (More info?)

    "Jason Haynes" <jasonlhaynes@COLDmail.com> wrote in message
    news:uiH$V1CnEHA.3352@TK2MSFTNGP15.phx.gbl...
    > With my limited knowledge of hyperthreading, I understand that a
    > hyperthreaded processor is seen as two processors and therefore the cpu
    > time in task manager is counting both processors simultaneously.

    Yeah, I understand that...but I just thought the figures displayed are
    misleading. It's like this machine is generating 2*X amount of hours worth
    of work in X hours....
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