Timers (was Trivial pc-speaker problem.)

Magnus Eriksson magetoo at fastmail.fm
Sun Sep 26 12:55:05 PDT 2004

On Sun, 26 Sep 2004, Joerg Sonnenberger wrote:

> On Sun, Sep 26, 2004 at 03:47:55PM +0000, Bartek Stalewski wrote:

> > Does anyone of You have working pc-speaker on FragonFly? ;-)

> You have to use "options TIMER_USE_1" for the speaker to work. Matt
> used the third (TIMER2) as primary system timer, but that means the
> wired lines to the speaker can't be utilized :)

  I'm a little curious.  What is the purpose of using multiple timers?

I've read what Matt said:

>    (TIMER0 is our fine-grained timer interrupt but TIMER1/TIMER2 is set
>    to a full-count and serves as the timebase for the whole system).

  ..but I'm not sure I get it.  So timer <not 0> is set for a longer
interval (for stability?) and timer 0 works "as usual"?

  But if I remember correctly, you don't have to reload the timers once
they are set up, so you have the long-term stability anyway,

  Or can timer 0 can be set for very short intervals, and timer <not 0> is
the one that "runs the OS" N times per sec?

  A simple non-technical answer will do.  Or just point me in the
direction of some part of the source that'll explain it.  (I did try to
find it, but boot code .. sigh.)


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