Re: New CBM-II discoveries

From: Michał Pleban <*lists_at_michau.name*> Date: Thu, 05 Jul 2018 12:34:00 +0200 Message-ID: <5B3DF418.4020103@michau.name> · lists_at_michau.name

smf wrote:

> From my point of view it is a big deal as you would have to have access
> to both types of hardware to write and test it. Maybe a situation you
> don't consider a problem because you do have both types of hardware.

You are right here, but again - if you want to develop something for the
original board with the 6523, the only thing you can use it for is to
communicate with the 6509 CPU, i.e. to implement another protocol for
inter-processor communication. Is that really worthwhile to do?

> The hassle you went through making the 8255 work because it's so
> different proves it would also limit some of the more exotic designs.

Yes, but the hassle was much smaller than re-creating the 6523 in a
CPLD. It was a trade-off, and both decisions had their upsides and
downsides. You have a valid point, but considering how unlikely is it
that someone would write another IPC protocol for the board, we decided
that using another chip had less downsides. It's a perfect solution, but
we feel that it was better.

Regards,
Michau.