Re: localtalk, was Re: pcmcia ethernet card support for m68k?
On Wed, Aug 12, 2020 at 05:54:29PM +1200, Michael Schmitz wrote:
> Finn is right - that's a baud rate, not bit rate. I'm a little hazy on
> whether SDLC uses start and stop bits at all - I'm guessing it does not,
> making baud rate almost equal to bit rate (not considering node address and
> prefix). Still close to 7.2 kHz interrupt rate.
OK. That makes sense. And I do believe you are right that there are
no start or stop bits. The charts I saw seem to indicate that there
is a start and stop tag for each end of the whole frame rather than
a bit on each data byte. The SCC docs also clearly indicate that
the address byte is just the first byte of data as well.
That interrupt rate still sounds like it could be hard to handle.
Perhaps it won't be quite as bad on some of the later models that
are running the CPU at higher clock speeds. At least we don't
support any of the 8MHz models. It might be more practical on some
of the PCI PowerMacs that are both running much faster CPUs and
have real DMA as well.
Brad Boyer
flar@allandria.com
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