From: Jesse Stockall <stockall@magma.ca>
To: linux@horizon.com
Cc: linux-kernel@vger.kernel.org, ACurrid@nvidia.com
Subject: Re: Clock inaccuracy seen on NVIDIA nForce2 systems
Date: Thu, 14 Oct 2004 08:09:17 -0400 [thread overview]
Message-ID: <1097755757.5114.7.camel@homer.blizzard.org> (raw)
In-Reply-To: <20041014012754.25198.qmail@science.horizon.com>
On Wed, 2004-10-13 at 21:27, linux@horizon.com wrote:
> > The system is running 2.6.9-rc4 and has been up for 2 days. I'm showing
> > an offset of -32 seconds and growing.
>
> That's -185 ppm (parts per million) error, or -0.0185%.
>
> Typical cheap quartz crystals are +/- 100 ppm, but there are some cheaper
> than that, and ceramic resonators like
> http://www.ecsxtal.com/cerares.htm
>
> I know Dave Mills learned from experience that the original +/-100 ppm
> specs in NTP weren't wide enough and he had to change it to cope with
> +/-500 ppm error in some clocks.
>
> It *could* just be your motherboard's clock source.
possible but....
a) When I boot without 'acpi_skip_timer_override' and I fall back to
using ExtINT for the timer there is no drift.
b) I rebooted and set FSB spread spectrum to 1.0 and let the machine run
over night. In 10 hours of uptime I'm off -45 seconds and growing. This
is -0.125%. So clearly having spread spectrum enabled does affect the
clock.
Thanks
Jesse
--
Jesse Stockall <stockall@magma.ca>
next prev parent reply other threads:[~2004-10-14 12:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-14 1:27 linux
2004-10-14 12:09 ` Jesse Stockall [this message]
-- strict thread matches above, loose matches on Subject: below --
2004-10-14 13:44 Francois Meyer
2004-10-13 20:30 Andy Currid
2004-10-13 21:10 ` Jesse Stockall
2004-10-14 0:45 ` Gene Heskett
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