MACC-II Motorola 6900 Computer

Lately I've been on somewhat of a Motorola 6800 kick. I've built the 68Retro MP-02A computer. A retro SWTPC like set of PCBs based on some of the SWTPC boards but modified. So not board compatible. Anyway, when I got my first job at Microcomm (which no longer exists) in East Brunswick NJ, I got to work with the SWTPC (6800), Flex, Gimix Ghost (6809) and OS9. This was just as the IBM PC clones began their dominance. We worked with a lot of Motorola chips and I learned a lot about computers, assembly language and electronics. Now I want to share some of the simpler times and what those devices were capable of.

With that in mind I found a 6800 based computer on EBay. I had hoped it was based on Motorola's EXORBUS, a bus standard that Motorola championed. But it wasn't. Still this computer, the MACC-II is an interesting relic from the 1980's. It's based on the Motorola 6800, has 4 6850 UARTs and a 6821 PIA. It has an odd interface to a WDC1771 Floppy controller. I think you need to access the 1771 via the 6821. Now work needs to be done there to reverse engineering this setup. Fortunately I found an app note which show a design with the 6821 and 1771. The computer also has a 9in. green monitor (composite?) accessed via a TTL video card (no video chip). I've copied the 2716 boot room. I need to work on accessing the 2708 (nasty triple voltage, a 2708 burner is on the way so soon ...). Anyway a lot more work to be done as the 2716 is a bit confusing where it's reading and writing.

Additionally the MACC-II needs a serial keyboard. I have a TeleVideo serial keyboard and hope to get that setup and working.

• Motorola 6800 - Wikipedia