APM causes system clock to "sleep"?
Andy Piper
I've just noticed that when I'm away from my machine, and the
BIOS APM features activate (e.g. hard disk spindown, monitor
power saving), the system clock 'stops'. Yesterday I noticed that
I seemed to 'lose' 15 minutes, and today I've been away for a few
hours and the time is currently showing as three hours behind.
I know the machine's internal clock is fine, because when I
rebooted yesterday the time was correct again (I also checked the
BIOS settings to confirm that it was all OK). Yet I have no way
of re-syncing the clock now without rebooting :-(
Is this a known "feature" of using power management? I'm running
kernel 2.0.36, and I've had absolutely no other problems
whatsoever, but in the longer term I don't want to have to reboot
my machine periodically in order to ensure that it gets its time
correct!
Andy
--
Andy Piper an...@argonet.co.uk
Fareham, Hampshire
Tarcus
Andy Piper <an...@argonet.co.uk> writes:
> I know the machine's internal clock is fine, because when I
> rebooted yesterday the time was correct again (I also checked the
> BIOS settings to confirm that it was all OK). Yet I have no way
> of re-syncing the clock now without rebooting :-(
This sounds rather strange! Have you got APM enabled in the kernel?
At any rate, read the manual page for the "clock" command, you can
re-read the hardware clock and set the software clock from it.
--
From the keyboard of Tarcus himself, running Linux in the UK.
-- There are no facts, only opinions --
eya...@novagate.com
: I've just noticed that when I'm away from my machine, and the
: BIOS APM features activate (e.g. hard disk spindown, monitor
: power saving), the system clock 'stops'. Yesterday I noticed that
: I seemed to 'lose' 15 minutes, and today I've been away for a few
: hours and the time is currently showing as three hours behind.
This problem is caused by the cpu speed throttling that APM BIOs uses
to lower the power consumption of the CPU. After a certain period
of inactivity the BIOs will make the CPU operate at a lower clock
frequency, or halt it's operation altogether. This greatly affects
the system clock since it counts clock cycles to determine elaspsed
time.
Unlike Win95/DOS, Linux uses the HLT instruction during idle loops
to reduce cpu power consumption, so speed throttling won't reduce
power consumption by much.
You can fix this problem by recompiling your kernel with APM mode
enabled, or you can simply disable CPU speed throttling in your
CMOS setup.
While you are at it, you might want to disable the hard disc
spindown too. The most wear on hard drives occurs during spin
up and spin down.
Andreas Hinz
>
>I know the machine's internal clock is fine, because when I
>rebooted yesterday the time was correct again (I also checked the
>BIOS settings to confirm that it was all OK). Yet I have no way
>of re-syncing the clock now without rebooting :-(
>
Ih ad the ssame problem when I first started using Linux. You have to
recompile the kernel with APM support.
--
Med venlig hilsen / Best regards
Andreas Hinz
Andy Piper
>
> On Wed, 06 Jan 1999 14:31:39 +0000, Andy Piper <an...@argonet.co.uk> wrote:
> >
> >I know the machine's internal clock is fine, because when I
> >rebooted yesterday the time was correct again (I also checked the
> >BIOS settings to confirm that it was all OK). Yet I have no way
> >of re-syncing the clock now without rebooting :-(
> >
>
> Ih ad the ssame problem when I first started using Linux. You have to
> recompile the kernel with APM support.
Strange... I could swear it *has* APM support. I'll check the
options I enabled when I replaced my old kernel with 2.0.36
recently!
Thanks - to everyone who replied :-)
Andy Piper
Tarcus <ia...@pobox.DUMPTHISBIT.quza.com> wrote in article
<770l2k$bjl$2...@lepto.tarcus.org.uk>...
> In article <369373CB...@argonet.co.uk>,
> Andy Piper <an...@argonet.co.uk> writes:
>
> > I know the machine's internal clock is fine, because when I
> > rebooted yesterday the time was correct again (I also checked the
> > BIOS settings to confirm that it was all OK). Yet I have no way
> > of re-syncing the clock now without rebooting :-(
>
> This sounds rather strange! Have you got APM enabled in the kernel?
Yes, I have. But there's also a load of BIOS settings for the level of
power saving to enable for hard disk spindown, etc., which I've set in the
machine's BIOS setup program.
> At any rate, read the manual page for the "clock" command, you can
> re-read the hardware clock and set the software clock from it.
Aha! Ding! I was looking at 'time' and 'date' to see if I could do
something similar. Thanks for the pointer.
Andy
--
Andy Piper
Technical Analyst, Middleware Development Group
phone: (01252) 528957 or (0780) 109 1431
e-mail: pip...@it.postoffice.co.uk or an...@argonet.co.uk
** All views expressed are my own! **