Michael Gardi's CPS-1 Is a Raspberry Pi-Powered Replica of a Near-Forgotten Canadian Classic

Retired software developer and vintage computing enthusiast Michael Gardi has built a replica microcomputer with a difference: nobody can really remember what the original, a Microsystems International CPS-1, looked like.

"Between 1972 and 1973, Ottawa based Microsystems International Ltd. (MIL) created CPS-1, the first Canadian microprocessor-based computer," Gardi explains. "They used their own MIL MP-1 chip set consisting of the MF7114 CPU integrated with MF1601 or 1701A ROM chips and MF7115 RAM chips. The CPS-1 supported a 12-bit address bus and a 4-bit data bus. It is unclear how many CPS-1 computers were produced and unfortunately, no CPS-1 computers have survived the intervening 50 plus years. In fact there are not even any photos of a CPS-1 available."

While there may not be any known surviving units, and no photos, the machine isn't entirely forgotten. Gardi got in touch with Zbigniew Stachniak, curator of the York University Computer Museum and author of a paper, which dove into the inner workings of the MF7114 processor that powered it. Stachniak's research was used to create a software-based emulator, complete with virtual toggle-switch front-panel — but Gardi wanted something more tactile.

"As the next phase of Zbigniew's research he had been thinking about implementing a hardware based front panel and asked if I might be interested in tackling this. Hell ya," Gardi recalls. "In the absence of an actual artifact or photo what does one do. Zbigniew started the conversation with a couple of items he had found among the documentation [including] part of a larger schematic for the CPS-1 that shows the position and functions of the switches and lights on the front panel [and] a low detail stylized image of the CPS-1 as it might have been."

These, already used to create the software emulator's virtual front panel, were used to inform Gardi's physical recreation — which uses modern switches with 3D-printed covers mimicking a period-appropriate design, installed in a professionally-produced panel and a 3D-printed replica of a Hammod 1401G housing. Inside the case is a Raspberry Pi 4 single-board computer with a general-purpose input/output (GPIO) expansion add-on to wire it to the front panel's switches and LEDs — which, in turn, control the York University Computer Museum emulator running on the Raspberry Pi itself.

"It was a lot of fun creating the CPS-1 reproduction," Gardi concludes. "I enjoyed working with Ziggy trying to deduce what the CPS-1 might have looked like. Regardless of how close we got with the 'look,' with the backing of the excellent York University Computer Museum (YUCoM) software based CPS-1 emulator, this is certainly going to be an excellent 'work a like' device."

The project is documented in full on Hackaday.io.