Re: localtalk, was Re: pcmcia ethernet card support for m68k?
On Thu, Aug 13, 2020 at 11:51:57AM +1000, Finn Thain wrote:
> This 26 ms interval will cause missed timer interrupts and system clock
> drift, unless the timer interrupt was polled too. (We could probably poll
> all of the VIA 1 interrupt sources for the duration of the packet, but not
> with Egret hardware because of delays in that interrupt handler.)
That will make for a really messy driver, but it could be done with some
careful thought. It could also be made conditional on m68k so that a
ppc based system wouldn't need it, since it can figure out how much
real time passed between timer interrupts with the timebase.
> Another consideration is raised in tech note TB 570. It says, "system
> services like AppleTalk require that interrupts not be disabled for much
> more than 1/1000th of a second usually. This means if you are doing
> something large during your interrupt routine (when all interrupts may be
> turned off), you could delay the AppleTalk interrupt so long that data
> gets lost."
>
> I think this is quite feasible for the majority of systems. A minority
> might drop some packets depending on hardware configuration, etc.
It sounds like the first step might be to audit all the other common
drivers to see which ones are disabling interrupts too long. I know
we do quite a bit of that.
Brad Boyer
flar@allandria.com
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