[LinuxBIOS] Timer frequencies

[Myles Watson]

I got Bochs to fail the same way the hardware (my Tyan s2892) fails when I
turned down the timer tick interrupt frequency.  I'm having trouble finding
the place where the timer gets set up.  (Grepping for time,rtc,timer,hz,
etc.)

Can someone tell me where I can make the interrupts come at 100 Hz in
LinuxBIOS?

Thanks,

Myles

[Marc Jones]

Myles Watson wrote:
> I got Bochs to fail the same way the hardware (my Tyan s2892) fails when 
> I turned down the timer tick interrupt frequency.  I’m having trouble 
> finding the place where the timer gets set up.  (Grepping for 
> time,rtc,timer,hz, etc.)
>
> Can someone tell me where I can make the interrupts come at 100 Hz in 
> LinuxBIOS?
>
> Thanks,
>
> Myles

I believe that you are looking for calibrate_tsc() in 
cpu\x86\tsc\delay_tsc.c. That only sets up channel2. No reason you 
couldn't make changes in your mainboard but I'm not sure the setting 
will stick. I would expect the linux kernel reprogram the PIT (maybe not 
if it is using ACPI timer or HPET)?

Marc

[Myles Watson]

> Subject: Re: [LinuxBIOS] Timer frequencies
> Myles Watson wrote:
> > I got Bochs to fail the same way the hardware (my Tyan s2892) fails when
> > I turned down the timer tick interrupt frequency.  I'm having trouble
> > finding the place where the timer gets set up.  (Grepping for
> > time,rtc,timer,hz, etc.)
> >
> > Can someone tell me where I can make the interrupts come at 100 Hz in
> > LinuxBIOS?
> >
> > Thanks,
> >
> > Myles
>
> I believe that you are looking for calibrate_tsc() in
> cpu\x86\tsc\delay_tsc.c. That only sets up channel2. No reason you
> couldn't make changes in your mainboard but I'm not sure the setting
> will stick. I would expect the linux kernel reprogram the PIT (maybe not
> if it is using ACPI timer or HPET)?

I'll check it out.  I'm actually booting Windows with ADLO, so I just need
to make it happy at boot time.

Thanks,
Myles
> Marc
>
> Marc Jones
> Senior Firmware Engineer
> [phone] Office
> mailto:[e-mail]
> http://www.amd.com/embeddedprocessors