RTC clock doesn't generate interrupts

[Peter Jeremy]

On 2007-May-20 18:26:30 +0200, Victor Balada Diaz <victor at bsdes.net> wrote:
>I have a server with FreeBSD 6.2 that is not generating RTC IRQs.
>When the system boots everything it's working fine and I get 128
>interrupts per second but after a few hours the system starts
>losing RTC interrupts. If I enable powerd it happens much faster
>than without it.

The RTC has a "feature" that if you ever lose an RTC interrupt
(because the interrupt handler wasn't called fast enough), you don't
get any more interrupts because the RTC knows it has an interrupt
pending and so doesn't generate any more interrupts.

I have also bumped into this problem whilst trying to work around
a problem with a TurionX2 CPU.  I just got the correct fix to work
and ignored the work-around.

I did find that you can restart the RTC interrupts by setting
machdep.adjkerntz (you can leave the value the same, it's the
assignment that's important).

Enabling powerd will reduce the CPU clock and so exacerbate any
problem you have with excessive interrupt latency.  I can't suggest
what might be the underlying cause of that latency.

-- 
Peter Jeremy
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