Re: real time clock running at double speed

Moe Trin wrote:
On Tue, 04 Sep 2007, in the Usenet newsgroup comp.os.linux.setup, in
article <1188897241.747805.172730@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, James
Kanze wrote:

NOTE: Posting from groups.google.com (or some web-forums) dramatically
reduces the chance of your post being seen. Find a real news server.

I've just installed the latest release of Mandrake Linux on a new
machine (Fujitsu-Siemens, with an AMD 5200 dual core processor).
Regretfully, the real time clock runs fast---what looks to be twice as
fast as it should.

Get your watch or a wall clock with a second hand. Run this command as
close to ten seconds apart ACCORDING TO THE WATCH as you can

[compton ~]$ grep ' 0:' /proc/interrupts 0: 75772989 timer [compton
~]$

Ten seconds later

[compton ~]$ grep ' 0:' /proc/interrupts 0: 75774014 timer [compton
~]$

75774014 - 75772989 == 1025

or about 1000 counts in ten seconds (you may see 10000 counts in ten
seconds, depending on how your kernel was compiled). Is this what you
see, or is it 2000 (or 20000) counts in ten seconds? If the later,
you've been caught with a well known problem - Configure your boot loader
to pass the parameter "noapic" as a kernel boot parameter.

For me, I get the following (two hyperthreaded processors):

$ grep ' 0:' /proc/interrupts
0: 592753979 592565242 594738059 594725854 IO-APIC-edge timer
$ grep ' 0:' /proc/interrupts
0: 592753979 592571220 594738059 594725854 IO-APIC-edge timer

Luckily, one processor (#1) got all the clock interrupts during this
interval of 0.1 minute -- 6 seconds -- the interval because my stopwatch
runs in minutes and hundredths. So I got 5978 ticks in about 6000
milliseconds or one tick per millisecond.

What if the O.P. needs APIC?

--
.~. Jean-David Beyer Registered Linux User 85642.
/V\ PGP-Key: 9A2FC99A Registered Machine 241939.
/( )\ Shrewsbury, New Jersey http://counter.li.org
^^-^^ 08:10:01 up 27 days, 11:32, 4 users, load average: 4.34, 5.09, 5.24
.

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