Re: pcmcia ethernet card support for m68k?
On Mon, Aug 10, 2020 at 10:29:07PM -0600, Stan Johnson wrote:
> On 8/10/20 8:03 PM, Finn Thain wrote:
> >
> > The way I see it, implementing Localtalk support, better FPU emulation or
> > any of a dozen other issues would be more rewarding because that might
> > help with lots of Mac models (particularly those with more RAM).
> >
>
> Supporting LocalTalk in Linux would be great for communicating with
> older Macs (and even better if you're talking about TCP/IP over
> LocalTalk, which would potentially allow Internet access via some
> LocalTalk/Ethernet bridges).
Do we have enough CPU time to implement LocalTalk fully in software
without causing other issues? I believe it's a synchronous protocol,
and unless you're talking about one of the models with IOPs (IIfx,
Q900, Q950) or real DMA (Q660, Q840) the CPU will need to be
involved on a very fixed schedule. Is it possible to do that level
of real-time scheduling with a standard Linux kernel? If I'm
interpreting the docs correctly, we will have to talk to the serial
controller around 8000 times per second (230kbit/s and 4 bytes at a
time from the ESCC) with very tight tolerances. Will it cause
problems to have the serial controller sending interrupts that
often? I suspect Apple just hogged the CPU during data transfer.
If we did have real LocalTalk support, we could use the ipddp module
to use a Linux box as the bridge. It has both modes according to the
code. I've never tried it myself, but it should work.
Brad Boyer
flar@allandria.com
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