Is the PIT unique?

AlfaOmega08 · Post by **AlfaOmega08** » Sat Sep 13, 2008 10:51 am

Very simply question?
Is there only one PIT for all processors wich are in your PC, or there is a PIT for each processor?

inflater · Post by **inflater** » Sat Sep 13, 2008 10:56 am

Only one I think... and has three channels: 0 (system timer), 1 (very old RAM refresh, not used now), 2 (tape drive and/or PC speaker)

Brendan · Post by **Brendan** » Sat Sep 13, 2008 12:22 pm

Hi,

Inflater is entirely right - there is only one PIT chip.

For multi-CPU systems there's a local APIC timer in each CPU you can use (which is far more precise anyway - I'd use it instead of the PIT in single-CPU systems if it's available), and it may be possible to configure the I/O APIC to send the PIT's IRQ to all CPUs at the same time (IIRC Linux did this in some cases, where the PIT's IRQ was configured as a "broadcast to all" NMI and used as a watchdog timer).

Cheers,

Brendan

AJ · Post by AJ » Sat Sep 13, 2008 4:11 pm

If you want to know about all time sources, don't forget that you have the RTC too.

Cheers,
Adam

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Is the PIT unique?

Is the PIT unique?

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