[Haiku-bugs] [Haiku] #1993: Implement using HPET timers and other mechanisms than TSC for time keeping

Haiku trac at haiku-os.org
Mon Mar 31 10:45:48 CEST 2008


#1993: Implement using HPET timers and other mechanisms than TSC for time keeping
--------------------------+-------------------------------------------------
  Reporter:  axeld        |       Owner:  axeld         
      Type:  enhancement  |      Status:  new           
  Priority:  high         |   Milestone:  R1            
 Component:  - General    |     Version:  R1 development
Resolution:               |    Platform:  All           
--------------------------+-------------------------------------------------
Old description:

> On CPUs that are able to change their frequency, the TSC increment is not
> invariant. Therefore, we cannot use it to compute time on these machines.
> Unfortunately, most recent CPUs are affected due to power saving
> features.
>
> Furthermore, in a SMP environment, the TSC of the different CPUs can
> drift apart. See http://lkml.org/lkml/2005/11/4/173 for an interesting
> insight on that topic.
>
> For HPET (and PM timer) see ACPI 3.0 specification
> http://www.acpi.info/spec.htm and
> http://www.intel.com/technology/architecture/hpetspec.htm

New description:

 On CPUs that are able to change their frequency, the TSC increment is not
 invariant. Therefore, we cannot use it to compute time on these machines.
 Unfortunately, most recent CPUs are affected due to power saving features.

 Furthermore, in an SMP environment, the TSC of the different CPUs can
 drift apart. See http://lkml.org/lkml/2005/11/4/173 for an interesting
 insight on that topic.

 For HPET (and PM timer) see ACPI 3.0 specification
 http://www.acpi.info/spec.htm and
 http://www.intel.com/technology/architecture/hpetspec.htm

-- 
Ticket URL: <http://dev.haiku-os.org/ticket/1993#comment:3>
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