From: "H. Peter Anvin" <hpa@zytor.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>, Ingo Molnar <mingo@elte.hu>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Alok Kataria <akataria@vmware.com>,
Arjan van de Veen <arjan@infradead.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [RFC patch 0/4] TSC calibration improvements
Date: Thu, 04 Sep 2008 11:30:47 -0700 [thread overview]
Message-ID: <48C02957.40708@zytor.com> (raw)
In-Reply-To: <alpine.LFD.1.10.0809041114030.3400@nehalem.linux-foundation.org>
Linus Torvalds wrote:
>
> Of course, the 2048 PIT ticks is just a random choice. It could be any
> multiple of 256 ticks, so that error can be made smaller. Maybe it's worth
> spending 10ms on this, and get it down by a factor of five (at which point
> the error on the PIT frequency is probably in the same order of
> magnitude).
>
FWIW, typical error on the 14.31818 MHz clock (used as the PIT, PMTMR
and HPET timebase in most systems) is usually ±50 ppm. High-quality
motherboards which use a TCXO for the 14.31818 MHz clock would have
around ±1 ppm.
-hpa
next prev parent reply other threads:[~2008-09-04 18:35 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-04 15:18 [RFC patch 0/4] TSC calibration improvements Thomas Gleixner
2008-09-04 15:18 ` [RFC patch 1/4] x86: TSC: define the PIT latch value separate Thomas Gleixner
2008-09-04 15:18 ` [RFC patch 2/4] x86: TSC: separate hpet/pmtimer calculation out Thomas Gleixner
2008-09-04 15:18 ` [RFC patch 3/4] x86: TSC: use one set of reference variables Thomas Gleixner
2008-09-04 15:18 ` [RFC patch 4/4] x86: TSC make the calibration loop smarter Thomas Gleixner
2008-09-04 15:36 ` [RFC patch 0/4] TSC calibration improvements Ingo Molnar
2008-09-04 15:45 ` Linus Torvalds
2008-09-04 16:00 ` Ingo Molnar
2008-09-04 16:21 ` Linus Torvalds
2008-09-04 16:36 ` Ingo Molnar
2008-09-04 17:41 ` Linus Torvalds
2008-09-04 18:07 ` Alan Cox
2008-09-04 18:26 ` Linus Torvalds
2008-09-04 18:30 ` H. Peter Anvin [this message]
2008-09-04 20:09 ` Linus Torvalds
2008-09-04 20:43 ` Ingo Molnar
2008-09-04 20:52 ` Ingo Molnar
2008-09-04 21:09 ` Linus Torvalds
2008-09-04 21:21 ` Ingo Molnar
2008-09-04 21:30 ` Linus Torvalds
2008-09-04 21:34 ` Linus Torvalds
2008-09-04 21:39 ` Ingo Molnar
2008-09-04 21:33 ` Ingo Molnar
2008-09-05 22:18 ` Alok Kataria
2008-09-05 22:34 ` Linus Torvalds
2008-09-06 20:03 ` Thomas Gleixner
2008-09-06 20:29 ` Linus Torvalds
2008-09-06 20:37 ` Thomas Gleixner
2008-09-06 20:50 ` Linus Torvalds
2008-09-06 20:55 ` Linus Torvalds
2008-09-06 21:15 ` Thomas Gleixner
2008-09-06 21:22 ` Linus Torvalds
2008-09-06 21:30 ` Thomas Gleixner
2008-09-06 22:40 ` Ingo Molnar
2008-09-06 20:58 ` Thomas Gleixner
2008-09-06 21:10 ` Linus Torvalds
2008-09-07 6:01 ` Willy Tarreau
2008-09-06 20:52 ` Thomas Gleixner
2008-09-06 20:59 ` Linus Torvalds
2008-09-06 21:07 ` Thomas Gleixner
2008-09-06 21:15 ` Linus Torvalds
2008-09-06 21:26 ` Thomas Gleixner
2008-09-06 21:32 ` Linus Torvalds
2008-09-04 20:53 ` Linus Torvalds
2008-09-04 21:38 ` Alok Kataria
2008-09-04 21:52 ` Linus Torvalds
2008-09-04 22:09 ` Alok Kataria
2008-09-04 17:39 ` Alok Kataria
2008-09-04 17:53 ` Linus Torvalds
2008-09-04 18:31 ` Alok Kataria
2008-09-04 18:34 ` H. Peter Anvin
2008-09-04 21:00 ` Valdis.Kletnieks
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