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Homebrew 8080 Multibus system (1978-79)
National Semiconductor SBC 80/10

The DigiBarn would like to thanks Richard Straka for this donation of a true example of a "homebrew" system (in this case an 8080 Multibus system). Such a system could well have been exhibited at the West Coast Computer Faire.

Notes from donor Richard Straka:

I have an old homebrew contribution that you might like. It's a National Semiconductor SBC 80/10 - based on the Intel "MultiBus" standard bus. As you're probably aware, this was an "industrial-strength" competitor to the S-100 bus. In about 1978, I stuffed a set of 4 boards that made up the computer. The CPU was an 8080 (1MHz?), and had the regular complement of parallel and serial I/O. 2 RAM cards, 16 KB each (4K 3-voltage (+5, +12, -5) DRAM chips). 1 ROM card. And a prototype card - good for things like interfacing an EPROM programmer (I was the product engineer for 2708 and 2716 EPROMs at National Semi in 1977-8), or tossing in some TTL logic and latches to make the machine boot at some address other than 0000 so that I could eventually get CP/M to run on it. (CP/M wanted RAM at 0000, not ROM as the system was designed. I got the boot change to work, but ran out of steam before I got to the CP/M stage. I got a Mac instead.)

I wirewrapped up a 24x80 video monitor for it (with an 8080 and a few EPROMS). The monitor put out composite video via a BNC connector. It ran at up to 600 bpS. After I shelved the computer project, I used the terminal to connect to my UNIX host at work (1982). I had to write my own termcap file for the terminal in order to use vi as a screen editor. Luckily, there wasn't much it did, so writing the termcap entry was very easy. I hobbled up a nice keyboard with a wood base and plexiglas top. The numeric keyboard had 0-F on it.

The system worked and ran a terminal monitor and Tiny Basic.
Some additions:

  • The card cage (duh)
  • Blueprints and some lightweight manuals for the cards.
  • The 3x5 index cards from which I made the wirelist for the monitor.
  • A paper tape of (as I recall) Tiny Basic and the old Star Trek game for Tiny Basic.
  • External EPROM programmer circuit board w/ ZIF socket (mounted on a chunk of 2x4)
  • 13" green on black monitor with contrast enhancing filter.
  • Power supply? I don't think so. It's big, open frame (1/8" ~12x18" aluminum base and has about 20-30 # of copper on it... Not shipping-friendly (cost-wise). But it fits in a traditional "book box".

I do have blueprints, schematics, application notes, some old paper tapes, wire list cards, etc. Whatever you want. This was strictly an OEM product. It has a nice, gray "filled nylon" card cage, but the plastic is sort of "U" shaped - so you can see about 1/2 the area of the frontmost board. The CPU board would be the most interesting looking, of course. No, they're not all that interesting unless you're a EE. The terminal board (separate) has an impressive amount of wire-wrap wire on it... The concept of a wire (node) list was a common technique from that era (and maybe still is today???). It's an inch-thick stack of 3x5 cards. The keyboard is definitely homebrew, but looks pretty decent considering. The hex digits on the numeric keypad is a nice touch.

Oh, and it takes +12, +5, -5 and -12. I still have the open-frame linear power supply which you can have if you need. I'd rather not ship it frankly, as it's probably 25-30 pounds in weight. But it's somewhat specialized in that I have a protection circuit to cut the +12 until the -5 comes up (otherwise, without -5v, those old dynamic RAM chips would really suck the power and self-destruct).

Images of this system

Whole system
Nice card case!
Extra chips
Wire wrapping under keyboard
Note cards & paper tape!
Star Trek game on paper tape
National Semiconductor
component guides

More circuit diagrams & notes

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