Tomas Pavlovic Brings Back a Czechoslovakian Classic, the Tesla PMI-80 Single-Board Computer

Built around Tesla's clone of Intel's 8080, this eight-bit microcomputer trainer lives again in fully-functional reproduction form.

Gareth Halfacree
1 month agoRetro Tech / HW101

Vintage computing enthusiast Tomas Pavlovic has designed a replica of the Tesla — no, not that Tesla — PMI-80 single-board computer, featuring as many period-appropriate parts as possible.

"PMI-80 was [an] educational computer produced by Tesla Piešťany, Czechoslovakia [in] 1982," Pavlovic explains of the original design on which his replica is based. "It was based on [Tesla's] MHB8080A, the clone of Intel 8080. It used 9-digit 7-segment LED display and 25-key hexadecimal keypad. Clock frequency was 1.111MHz. It had 1kB of ROM with 'operating system' MONITOR. It was possible to add another 1kB of user ROM. Next it contained 1kB of RWM (read–write memory)."

Designed, like so many microprocessor systems of the era, more for educational and experimental use than truly practical computing, the original PMI-80 was not readily available outside Czechoslovakia — now the sovereign states of the Czech Republic and Slovakia. Pavlovic's recreation, then, aims to offer a broader distribution while working around a few missing pieces in the puzzle.

"I tried to use as many original Tesla parts as possible," Pavlovic explains of the replica PMI-80. "The keyboard used in [the] original was [a] modified calculator keyboard from OKU-205. It is not possible to obtain it so I designed my own keyboard from two PCBs, bottom with switches and top as a overlay. The replica also contains original MONITOR software. The power supply must provide three voltages +5V, -5V, and +12V, which is common for 8080 designs."

The MONITOR serves as a proto-operating system for the system, loading from ROM and allowing the user to enter program code step-by-step using the hexadecimal keypad to enter the Intel 8080 instructions one-by-one. "Although it is very tedious to enter any code to this computer," Pavlovic admits, "it is [a] great tool to learn how computer work."

More information on the project is available on Pavlovic's GitHub repository, while kits featuring all components bar the power supply are listed for sale on Tindie — though, at the time of writing, were showing as out of stock.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
Latest articles
Sponsored articles
Related articles
Latest articles
Read more
Related articles