[sdiy] Xpander (was: Re: Moog Memorymoog clone almost completed)

[Brian Willoughby]

On Oct 17, 2020, at 11:24 AM, Michael Zacherl <sdiy-mz01 at blauwurf.info> wrote:
> On 16.10.2020, at 23:38, MTG <grant at musictechnologiesgroup.com> wrote:
>> What CPU did Oberheim switch to for Xpander? Is that 6809?
> 
> 2x 6809 (one main, one for the voices) - IIRC.
> m.

Yes, and the Matrix-12 has 3x 6809 (one main, one for each of the 6-voice boards)

As I noted a while back, there are pins on the main board that could allow four 6-voice boards to be attached, but that feature was never developed. Such a beast would have 5x 6809.

I believe that the main CPU writes directly into the memory space of the voice CPU. i.e. there are no "MIDI" messages exchanged with the voice boards, but direct memory modification. I need to look into that a little deeper.

Brian