Re: [gentoo-user] clock problems software clock 20x fast

[Richard Fish <bigfish@asmallpond.org>]

On 12/14/05, Noah J Norris <preludelinux@mchsi.com> wrote:
> On Wednesday 14 December 2005 05:39 pm, Richard Fish wrote:
> > 1. Make sure that the first line of /etc/adjtime contains very small
> > values.  In fact, you might just want to replace the first line with
> > "0.0 0 0.0".
> i tried changeing this is this for the hardware clock drift ? i dont have any
> problem with the hardware clock its the software clock thats fast

Oh, you are correct.  Sorry.

> >
> > 2. Take a look at the clock= settings in
> > /usr/src/linux/Documentation/kernel-parameters.txt.  Maybe you need
> > clock=pit.
>
> looking in this file saw some other options that may help the problem.
> i have an ati chipset (newer laptop chipset) ouput of lspci below
>

<snip>

>
> some options i saw in that file that i may try
>
> acpi_skip_timer_override [HW,ACPI]
>                         Recognize and ignore IRQ0/pin2 Interrupt Override.
>                         For broken nForce2 BIOS resulting in XT-PIC timer.
>
> enable_timer_pin_1 [i386,x86-64]
>                         Enable PIN 1 of APIC timer
>                         Can be useful to work around chipset bugs
>                         (in particular on some ATI chipsets).
>                         The kernel tries to set a reasonable default.
>
>         disable_timer_pin_1 [i386,x86-64]
>                         Disable PIN 1 of APIC timer
>                         Can be useful to work around chipset bugs.

I'm not sure these will help.  They seem to be more related to setting
up the frequency for the IRQ0 timer interrupt, for things like running
the scheduler.  This should not be related at all to the behavior of
gettimeofday.

I think if you were getting messages about lost ticks or got extra
ticks or something like that, these might be helpful, or if your
system seemed either to slow or too unresponsive.  Of course, if your
clock is defaulting to TSC (which would be bad, BTW), then I guess
these could have a big impact.

Take a look at dmesg or /var/log/messages for the following lines:

Using TSC for gettimeofday
Using HPET for gettimeofday
Using .* for high-res timesource

These will tell us what signal the kernel is using for gettimeofday on
your system.

-Richard

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