RE: 6809 in a C64

Hallo Jim,

Looks very promising!

Met vriendelijke groet / With kind regards, Ruud Baltissen

www.Baltissen.org<http://www.Baltissen.org>



From: Jim Brain <brain@jbrain.com>
Sent: woensdag 23 mei 2018 08:10
To: cbm-hackers@musoftware.de
Subject: 6809 in a C64


Ruud:

In reference to this old posting:

http://www.softwolves.com/arkiv/cbm-hackers/13/13116.html


I thought I'd note that I designed a C64 cartridge containing a MC6809 and some RAM.  I know it's not exactly the same as your idea, but it is easier to prototype.

https://www.facebook.com/go4retro/photos/a.386509271508869.1073741826.386509238175539/984731561686634/?type=3&theater


The initial goal is to multiplex the two CPUs, allowing the 6809 to access some shared RAM on the low PHI2 portion of the cycle, and 64 access on the high portion.  Then, I'll try to speed up the 6809 to 4MHz and see if I can keep the shared memory in place.

Possibly later, I'll see if I can have the 6809 take over the bus like SuperCPU and Chameleon64, but I suspect I have to learn quite a bit more about the system bus.

Jim



--

Jim Brain

brain@jbrain.com<mailto:brain@jbrain.com>

www.jbrain.com<http://www.jbrain.com>
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