MULTIPROCESSING FOR THE IMPOVERISHED Part 1: a 6809 Uniprocessor

[Eric Smith]

On Fri, Aug 2, 2019 at 11:15 AM Liam Proven via cctalk <
cctalk at classiccmp.org> wrote:

> 1993 article on building a multiprocessor 6809 box.
> http://www.bradrodriguez.com/papers/6809cpu.htm
>

I disagree very much with the author's advice to use the MC6809 rather than
the MC6809E. With the E version you have to supply a quadrature clock, but
all that's required to generate that is a single-phase 4x clock (which you
need with either the E or non-E part) and a single 74HCT74. If you feed
your single-phase 4x clock into multiple 6809 (non-E) parts, their E clock
phases won't match, but will be off by arbitrary multiples of 1/4 cycle,
which makes the shared memory design unnecessarily difficult.