The H2Z80 Is a Zilog Z80-Based Compact Microcomputer Built Entirely on Perfboard

Powering its own color display, this hand-wired microcomputer packs a lot into a very small footprint.

Gareth Halfacree
1 month agoRetro Tech / HW101

Pseudonymous army officer and retrocomputing enthusiast "Jorisclayton" is building a Zilog Z80-based home computer with a difference: as its name suggests, the Homebrew Handwired Z80 Computer is all hand-wired on perfboard, no custom printed circuit boards required.

"This little computer idea was born from my desire to better understand how computers really work and how they can do everything they actually do," Jorisclayton explains of the H2Z80. "The thing started very slow… as anyone can imagine, understanding how to build it from zero is quite difficult and I don't have any training to do that."

Like many of the classic computers of the 1970s and 1980s from which Jorisclayton drew inspiration, the H2Z80 is built around Zilog's eight-bit Z80 microprocessor — a device the company has only recently announced it will discontinue in standalone CPU format, though it lives on as an embedded device. There's 64kB of RAM and a 32kB ROM, currently used to run a monitor and boot a copy of Digital's CP/M 2.2 operating system.

To see what's going on the system includes a video output board which is driven by a Texas Instruments TMS9918 Video Display Processor (VDP) with 16kB of dedicated video RAM. "This board also provides the connections for stereo audio and power to a small RCA monitor that I have here," Jorisclayton adds, "and has its own 5 volts regulator."

Two more expansion slots are filled by a CompactFlash storage board with status monitor and a PS/2 keyboard and joypad adapter board — the latter of which is still, Jorisclayton admits, a work in progress.

More details on the project, including an unfinished schematic, are available on Jorisclayton's Hackaday.io page.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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