In message <199603111346.IAA24975@puma.bevd.blacksburg.va.us>,Allen Briggs writ
es:
>...
>same and lower levels.  So if you're running at level 2 due to a level 2
>interrupt, you will not receive other level 2 or any level 1 interrupts,
>but you might receive level 3-7 interrupts.  On the mac, level 1
>interrupts are from VIA1, level 2 from VIA2/RBV, level 4 from the SCC,
>and level 7 from the debugger (NMI) switch.  The SCSI and ethernet
>(NuBus) interrupts are on VIA2.  Most everything else is on VIA1.  If
>any interrupt handler is running, it's masked off the clock interrupts.
>...

you dont mention level 5 or level 6 -- could we move the clock to 
one of those?  are these the via general purpose timer interrupts?

>Now, it might be a good idea to keep track of the RTC and slew the
>NetBSD clock.  I haven't come up with a good algorithm for that, yet,

i imagine doing the same thing as sys_adjtime() is what we want.  see
sys/kern/kern_time.c.

>Yes.  One option you didn't mention is to do a sort of software masking
>of interrupts and basically put all interrupts on the same priority

evil.