A Tandy / RadioShack TRS-80 Model 1 clone

A clone of TRS-80 by Glen Kleinschmidt, who also did a Commodore PET-2001 clone.

Following is from the PDF document describing the clone:

[T]his clone is a functional replica of the original computer in the traditional hardware sense. It’s not an FPGA port or an emulator running on a Raspberry Pi and nor is it a part-for-part duplication of the original circuitry, but a complete ground-up re-design using contemporary discrete CMOS logic and memory devices, with some additional features thrown in for good measure. At the time of writing every component used in this project is a current-production part.


The documentation is definitely worth a read, it’s well-written and describes both a number of design choices in the original design and choices made in cloning.

I particularly enjoyed the discussion of the baroque character generation in the original hardware.

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Agreed, a workalike rebuild with modern and available parts has an attraction. Chris Smith’s Harlequin project did this for Sinclair’s ZX Spectrum - quite a feat because that machine contains custom silicon, as well as dodgy tricks to make a dual-master bus. (By dodgy tricks I mean resistors.) Chris also wrote an excellent book on the workings of the Spectrum, containing many insights on the implementation.



And huh … I never realized the original TRS-80 font was only 6 pixels wide (5 pixel wide characters with an extra blank column). I’ve never actually seen a Model I - just lots of Model III’s in schools and Radio Shacks. The Model III had a different font, and I think each character occupied a space that was 8x12 pixels on them (so the pixel width would be 8 x 64, not 6 x 64)

I think I might need to build one of each.