Classic computing fanatic Marcel Erz is bringing again the Tandy-Radio Shack TRS-80 residence laptop — with a trace-for-trace reimplementation of the unique Mannequin I motherboard, launched underneath a permissive license.
“This mission is a devoted reimplementation of the mainboard of the long-lasting TRS-80 Mannequin I (Revision G) laptop,” Erz writes of his work. “My very own revision, the E1, is designed to copy the unique system’s performance through the use of a PCB design 1-to-1 to the unique, together with elements, interfaces, and even traces. Your complete mission is on the market underneath the MIT license.”
Marcel Erz is bringing the TRS-80 microcomputer again in type, with a lovingly-cloned and fully-compatible motherboard. (📷: Marcel Erz)
Launched by Tandy in 1977 and bought via its Radio Shack shops, therefore the letters “TRS” in its identify, the TRS-80 Mannequin I used to be a Zilog Z80-based eight-bit residence laptop with 4kB of RAM, upgradeable to 48kB in 16kB steps, and was a serious hit for the corporate — changing into not solely one in all its greatest sellers however the best-selling residence laptop of its period, spawning a variety of suitable follow-ups together with the famously transportable TRS-80 Mannequin 100.
Whereas its best-selling nature and quite a few follow-ups imply that they don’t seem to be the rarest issues round, unique TRS-80 Mannequin Is are undoubtedly displaying their age — which is the place Erz’ “E1” is available in. The board, designed in KiCad 7, is a devoted reproduction of the unique — even right down to unused vias and holes used throughout Tandy’s unique manufacturing course of to maintain the boards in place. Different errors, together with a further capacitor not documented within the machine’s reference guide, are fastened within the new design.
The board is designed to imitate, as carefully as doable, the unique Tandy design (pictured). (📷: Binarysequence, CC-BY-SA 4.0)
With the intention to flip the PCB right into a fully-functional TRS-80 Mannequin I, you may want elements — and right here Erz’ work features a full invoice of supplies. Every thing is constructed to the unique specification, that means period-appropriate elements would be the order of the day — although in lots of instances fashionable equivalents can be found, whereas different elements will should be sourced from previous inventory or discarded units. A set of ordering directions can be offered “to get a extra devoted model of the board,” Erz says.
The mission’s design information can be found on the RetroStack GitHub repository underneath the permissive MIT license.