Re: pcmcia ethernet card support for m68k?
On Wed, 12 Aug 2020, Michael Schmitz wrote:
>
> Depends on the interrupt priority levels - if the SCC can preempt other
> interrupt handlers, and you do nothing but acknowledge the interrupt and
> copy bytes to a buffer, this might be worth a try.
Is there overhead in monitoring packets for node addresses? If so, any
node on the network would consume CPU of every other node whenever it
transmits... if true, it begs for IOP offload (or DMA).
> Protocol handling and moving buffer data to network buffers would be
> left to a task queue, to run when a packet has been fully received.
>
> Today's kernels are a lot smarter with locks than 20 years ago when this
> would have been impossible.
>
> How large are the data packets involved? Is there a pseudo-DMA address
> window for the SCC data port to used optimized access (moveml)? Does SCC
> access force a bus delay, or can the SCC be accessed at full rate?
>
Good questions. But I'm not going to dive into leaked source code or
disassembled drivers to find answers. I might dig out the relevant books
and tech notes though.
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