Intellec MDS-800 and related Multibus stuff

[sysadmindave]

I would love to get any info on the Z-80 CPU Multibus board. That would be a great one to build a Multibus system around.

After doing some more digging around this morning, I found the documentation for that Z80 board included in a binder in one of the boxes- I was wrong about the vendor that made it. I also found I have 2 of those boards (and 2 of the manuals). They were built by Monolithic Systems as a single-board computer system- apparently they did a whole line of these with differing capabilities. There's a manual online for a similar card (later one, it looks like) at bitsavers.org. It includes schematics and LOTS of information, since it was targeted at engineers that wanted to integrate it. I have quite a bit of documentation, but unfortunately the Winchester Systems manuals were in a box that got wet at some point and are completely ruined to the point of unreadability. The documentation does include some sales material which is interesting also.

 

[sysadmindave]

More goodies!

Several of these are boards specifically made for the piano controllers. There are 4 custom boards in the piano controllers: Z80 processor board, serial communication board, 'actuator interface', and 'keyboard interface', and I think all of those are here. In addition, there's a custom galvanometer control board for a laser scanner of some kind that Wayne built, and a number of development revs of a processor card based on the Zilog Z280 (one pictured here). I believe the Z280 board was for a revision to the piano that never actually happened- Wayne mentioned that the Z280 chip itself was quite buggy.

I think with this batch I have uploaded photos of all of the types of Multibus boards- I have duplicates of a number of them. Also included were some EPROM and PAL programming hardware and a number of EPROMs and EEPROMs.

Much of this equipment doesn't pre-date the Altair, so maybe this is in the wrong forum, but the MDS-800 certainly does, so?

I will try to scan some of the loose and 3-ring bound documentation soon.

 

[MykeLawson]

Thanks for the link to the bitsavers info. Looks like some quiet time reading through it will be in the plan soon. If I'd ever wind up respinning a new version of this, I'll have to figure out how to engineer the 'programmable' devices out of the circuit, to configure it to use SRAM vice DRAM, and work with newer EPROM devices. If I could get that done I'd have the trifecta of retro computers; STD, S-100, and Multibus (all Z-80).... Sweet!

 

[hjohnson]

Dave, you'll decide on your course of actions for these systems. But it's plausible to bring up at least one of the Multibus boxes or cages to operate the hardware, at least to access the diskettes. The Zendex ZX-200 is documented on bitsavers. It's a unique floppy controller in that it emulates the Intel M2FM two-board system they used for their initial version of double-density floppy control; *and* it has a FDC single-chip floppy controller, my guess for support of ordinary FM single-density which Intel also used early.

INtel M2FM is unique even among other M2FM implementations. It has has had considerable discussion and action in the Google Group intel dev-sys. INtel FM is the same as other's FM 8-inch "IBM 3270 format". Diskette and file recovery has had much discussion in dev-sys The Zendex has had mention there and is desirable but hard to find. My good friend Jon Hale rightfully directs your attention to that group of Intel development system recover-ers. They've seen this movie before. I'm mostly a cheerleader there.

It's a great opportunity when someone finds an early development system environment of hardware, manuals and disks. I hope you can restore at least one development computer and also the piano application, which of course is a great interest of yours. The keyboard pickup scheme and management, is a great engineering exercise. Hope you can restore some part of some (piano) keyboard segment.

Vintage computing of the 1970's and early 80's, looked at today, overly focuses on consumer class computing. But it all began before that, as development and application and business/industrial systems like these. Moreso, when development hardware often became the application hardware. While this hardware is post-Altair more or less, it's pre-consumer computing (CP/M notwithstanding) and M2FM is early days certainly. Where you choose to move the thread is your call, but unless there's a more Multibus-specific forum, "pre-Altair" isn't a bad place. But I don't use these forums enough to have a vote.

regards Herb Johnson
retrotechnology.com

 

[sysadmindave]

Thanks Herb for your gracious and well-informed reply. I really appreciate the expertise and respect here and in the general retro-computing community.

I have taken the excellent advice given by Jon and joined the intel-devsys Google group, and have learned a considerable amount about this equipment since it arrived in my hands. I have yet to attempt to power any of it, still working through inventory and planning what to do next, and trying to fit it in to work schedules etc., so it's getting short shrift at the moment.

It seems to me that this is a significant selection of early microcomputing hardware, software, and documentation, so I'm really wanting to be sure that I do no harm to any of it and archive what I can of EPROM contents and floppies as soon as I can get to it. I definitely like that this set of systems have a story and I know what they were used to develop.

I think that before I even attempt to power up any of the Multibus stuff I want to capture disk images with the Greaseweazel- I don't have the 34-pin to 50-pin edge-card adapter that I ordered just yet, but hope to have it shortly so I can work on getting one or more of the floppy drives up and running that way. There are other MDS-800s and Multibus systems, but some of the firmware, software and data may be unique.

I can then concentrate on the Multibus development equipment in isolation after I safely archive the floppy contents. I don't think I can access the HD with anything other than the MDS-800 though.

I'm hoping to get both ISIS (II?) and CP/M bootable on the MDS-800 and maybe the Monolithic Systems' setup. I also saw in the Google group that Eric Smith was looking to reverse engineer a Zendex ZX-203 a few years ago, so I've offered to lend him one of the two from this collection. Interestingly, Wayne was not a fan of these controllers and cautioned me that they corrupted floppies for him on multiple instances.

I might keep future contributions to this thread more limited to the MDS-800 system itself since it's the earliest and most on-topic. I do find myself fascinated by this early hardware, especially since it was targeted at engineers. The documentation seems excellent!

 

[sysadmindave]

Very cool! Would you be willing to make a new post on your instrument with photos/videos?

New post on the piano is here. I'll upload some videos to box.com and link them in that thread hopefully later this week.