From: john stultz <johnstul@us.ibm.com>
To: Joris van Rantwijk <joris@eljakim.nl>
Cc: lkml <linux-kernel@vger.kernel.org>, Dominik Brodowski <linux@brodo.de>
Subject: Re: System clock speed too high - 2.6.3 kernel
Date: Tue, 25 May 2004 13:53:42 -0700 [thread overview]
Message-ID: <1085518422.8653.14.camel@cog.beaverton.ibm.com> (raw)
In-Reply-To: <Pine.LNX.4.58.0405251112040.30050@eljakim.netsystem.nl>
On Tue, 2004-05-25 at 02:22, Joris van Rantwijk wrote:
> On Fri, 26 Mar 2004, Praedor Atrebates wrote:
> > I have Mandrake 10.0, kernel-2.6.3-7mdk installed, on an IBM Thinkpad 1412
> > laptop, celeron 366, 512MB RAM. I am finding that my system clock is ticking
> > away at a rate of about 3:1 vs reality, ie, I count ~3 seconds on the system
> > clock for every 1 real second. I am running ntpd but this is unable to keep
> > up with the rate of system clock passage.
>
> I have the same problem with kernel 2.6.6, only in my case the speed is
> exactly doubled (not 3:1). Saying "clock=tsc" at boot time solves this
> perfectly.
>
> My mainboard is Asus P5A (4 years old) with ALi M1541 chipset.
> Linux detects a PM-Timer at port 0xec08. I measured the counting rate
> of this port (while safely running with clock=tsc) and it comes out at
> about 7159155 ticks per second. The rate expected by
> arch/i386/kernel/timer/timer_pm.c is 3579545 ticks per second, so this
> explains the double speed very nicely.
>
> Perhaps this should be documented in the kernel config info.
> If there are many systems with this problem, then calibrating the PM timer
> against the PIT timer at boot time (possibly rejecting invalid rates)
> might be an option.
Check out bugme bug #2375. Some systems have ACPI PM timers that run too
fast. Running w/ "clock=tsc" is the proper workaround, but we need to
blacklist such systems from using it. If you could add dmidecode output
to the bug, I'll add your system to the list.
http://bugme.osdl.org/show_bug.cgi?id=2375
thanks
-john
next prev parent reply other threads:[~2004-05-25 20:53 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1E4zj-77w-69@gated-at.bofh.it>
2004-05-25 9:22 ` System clock speed too high - 2.6.3 kernel Joris van Rantwijk
2004-05-25 20:53 ` john stultz [this message]
2004-05-25 20:58 ` john stultz
2004-05-26 22:43 ` Joris van Rantwijk
2004-05-26 23:08 ` john stultz
2004-05-27 21:35 ` [PATCH] 2.6.6 Validate PM-Timer rate at boot time Joris van Rantwijk
2004-05-27 13:32 ` System clock speed too high - 2.6.3 kernel Bill Davidsen
2004-03-26 19:30 Praedor Atrebates
2004-03-26 21:22 ` john stultz
2004-03-26 21:54 ` Praedor Atrebates
2004-03-26 23:09 ` john stultz
[not found] ` <200403261800.32717.praedor@yahoo.com>
2004-03-26 21:57 ` john stultz
2004-03-26 22:05 ` Praedor Atrebates
2004-03-26 22:18 ` Praedor Atrebates
2004-03-30 15:25 ` john stultz
2004-04-06 21:46 ` Dominik Brodowski
2004-03-26 21:46 ` George Anzinger
2004-03-26 21:57 ` Praedor Atrebates
2004-03-27 16:09 ` George Anzinger
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