The Sinclair ZX80

ZX80 Revisited

With its unique place in computing history, there is still a lot of interest in the ZX80 and, being entirely built from discrete logic components, with no custom logic chips (other then the contents of the ROM), it is even possible to build your own!

Grant Searle has comprehensive details on building your own ZX80, either on strip-board, or on a recreated PCB, on his ZX80 homebuilt hardware page.

	Click to open full size image
Martin Allcorn used this information to build a ZX80 on a Eurocard prototyping board, using currently available parts.
A nice feature of Martin's version is that it has both the ZX80 and ZX81 ROM contents in the ROM chip. The red jumper block switches between the two ROMs, and the 4-pin header is for the 5VDC power input.
Screen shot from the board running Sinclair BASIC - with the screen output in reverse video. The light stripe across the bottom of the screen is, unfortunately, a "feature" of the design.
The output levels from the board are such that normal video is not displayed correctly on a TV screen - inverse video output is much improved. The green jumper next to the Z80 CPU switches between normal and inverse video.
Running with a copy of the original 4k ROM selected
Running with the 8k ROM selected
Photo showing the system running from the "external PSU" and connected to Martin's "home brew" keyboard.
Keyboard close up
Pictures and other information courtesy of Martin Allcorn