(Retro) Single-board computers

Single-board computers from the early microcomputing era have always fascinated me. Oft-unhoused machines resembling motherboards with calculator-esque keypads and a handful of seven-segment LEDs for a display1, their purpose was to train prospective engineers on the operations of new microprocessors like the Intel 8080 and MOS 6502. Some, like MOS’s KIM-1 were quite affordable, and gave hobbyists a platform to learn on, experiment with, and build up into something bigger.

The KIM-1 is, to me, the archetypal single-board. Initially released by MOS and kept in production by Commodore, it had a six-digit display, 23-key input pad, 6502 processor, and a pair of 6530 RIOT chips. MOS pioneered manufacturing technology that allowed for a far higher yield of chips than competitors, making the KIM-1 a device that hobbyists could actually afford. I would love to acquire one, but unfortunately they are not nearly as affordable these days, often fetching around $1,000 at auction. Humorously, clones like the SYM-1 that were far more expensive when they were released are not nearly as collectable and sell at more reasonable rates. Even these are a bit pricy, however, and you never know if they’ll arrive operable. If they do, it’s a crapshoot how long that will remain true.

Other notable single-boards like the Science of Cambridge (Sinclair) MK14 and the Ferguson Big Board rarely even show up on eBay. The MK14 is another unit that I would absolutely love to own – I have a soft spot for Clive Sinclair’s wild cost-cut creations. This seems extremely unlikely, however, leaving me to resort to emulation. Likewise for the KIM-1, a good emulator humorously exists for the Commodore 64.

History has a way of repeating itself, I suppose, and I think a lot of that retro hobbyist experience lives on in tiny modern single-board computers like the Raspberry Pi and Arduino. I’m glad these exist, I’d be happy to use one if I had a specific need, but they don’t particularly interest me from a recreational computing perspective. Given that these modern descendants don’t scratch that itch, and the rarity and uncertainty of vintage units, I was very excited to recently stumble across Thai engineer Wichit Sirichote’s various single-board kits for classic microprocessors. Built examples are available on eBay. The usual suspects are there: 8080, 8088, 8086, Z80, 68008, 6502; some odd ducks as well like the CDP1802.

I have ordered, and plan to write about the cheapest offering: the 8051 which sells in built form for $85, shipped from Thailand. The 8051 was an Intel creation for embedded/industrial systems, and is an unfamiliar architecture for me. If it all works out how I hope it will, I wouldn’t mind acquiring the 6502, Z80, CDP1802 and/or one of the 808xs. I’d love to see a version using the SC/MP (as used in the Cambridge MK14), but I’m not sure there are any modern clones available2. For now, I will do some recreational experiments with the 8051, perhaps hitting a code golf challenge or two. While this can’t be quite the same as unboxing a KIM-1, I love that somebody is making these machines. And not just one or two, but like… a bunch. Recreational computing lives.

  1. I guess machines like the Commodore 64 were technically single-board, lacking internal expansion mechanisms. But I’ve only really heard people referring to the training devices as such. ↩︎
  2. I’ve done a small amount of searching, and… there don’t seem to be. And original chips fetch $$$ at auction. Which is a real shame, because the SC/MP was a very early chip that supported, in some sense, multiple processors. That would be very, very neat to fuck with. ↩︎