[ntp:questions] Re: announce: PPSkit-2.1.2 for Linux 2.4.21

Ulrich Windl Ulrich.Windl at RZ.Uni-Regensburg.DE
Fri Sep 5 11:10:12 UTC 2003


ptrojane at mion.elka.pw.edu.pl (Piotr Trojanek) writes:

> In article <bj7s76$sbd$1 at mc-pc.research.telcordia.com>, Allen McIntosh wrote:
> >In article <slrnblbemk.bq7.ptrojane at mion.elka.pw.edu.pl>,
> >Piotr Trojanek <ptrojane at mion.elka.pw.edu.pl> wrote:
> >>What are the reasons Linux use TSC for PPS timestamping, while
> >>FreeBSD-5.1-RELEASE use ACPI (by default)? -- I don't say ACPI is
> >>better, just asking.
> >
> >Maybe because more machines have TSC?
> 
> true, but only for "old" Pentium 100MHz and similar.
> every modern PC I saw has both TSC and ACPI.

Today I rebooted the backup timeserver, a Intel 386/SX 16MHz with 8MB
RAM (maximum possible) and a PIO IDE drive... ;-)

The machine has no TSC, nor APIC, but is still works. It's one of the
last quality computers being built...

Regards,
Ulrich

> 
> but on FreeBSD you can change used hardware on fly with:
> sysctl kern.timecounter.hardware=[ACPI-fast|TSC|i8254]
> 
> (this is for 5.1-RELEASE, on 4.[78] sysctl variable was
> diffrent, and no ACPI-fast was possible).
> 
> -- 
> Piotr Trojanek



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