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

Piotr Trojanek ptrojane at mion.elka.pw.edu.pl
Fri Sep 5 08:01:49 UTC 2003

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.

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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