From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Tue, 28 Apr 2009 07:50:28 +0200
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: [Xenomai-core] xenomai 2.5 rc1 timing computations.
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Hi,

currently, the situation is this:
- the timing core uses an approximate value of the cpu frequency (using
xnarch_llmulshft) to do conversions between tsc and ns;
- the APIC timer reprogrammation still uses imuldiv, that is a more
exact cpu frequency, coupled with an approximate APIC frequency
(obtained from ipipe_request_tickdev), to do the conversion between tsc
delays and APIC delays;
- the posix skin uses llimd to do conversions between timespec and
timeval structures and tsc values
- the posix and native skins in user-space still use llimd to do
conversions between ns and tsc (only if using tsc in user-space).

These are causes of unprecisions, I think we should fix this, though it
is unlikely to be the cause of the high jitters observed by Vikesh with
2.5-rc1.

Regards.

-- 
					    Gilles.