- Stephen Nichol
Three Z80 Computer Kits You Can Buy & Build Today
Made by a breakaway group from Intel, the Z80 processor was an enhancement of Intel's (who later gave the world the Pentium processor) own 8080, using different names for it's instruction set to cover Zilog's posterior legally.
Features such as built in Dynamic-RAM refresh (DRAM was significantly cheaper than Static-RAM in the late 1970's and early 80's) helped the chip find it's way into many 8-bit devices of the time, such as the Sinclair ZX80, ZX81, and ZX Spectrum, the Amstrad CPC464, MSX and - near the end of the 1980's - the Nintendo Gameboy (in a custom form).
It's use continued into the 1990's, with the Z80 re-purposed as a Graphics Processor Unit in the SEGA Megadrive, and the Z80 went all the way up to 24-bit in later incarnations created and sold by Zilog into the mid to late 2000's.
Building a homebrew computer is a fairly popular hobby among the retro community, and why not? What railway enthusiast would pass up the chance to build a full-size replica steam engine, or car collector the opportunity of building a kit of a Model T-Ford or aircraft-without-wings sports car?
The Z80 is a popular choice today, and well documented - with a plethora of books, datasheets, websites, and videos to study - fairly simple to understand (The 1980's Amiga and ST's Motorola 68000 is called a CISC chip for a reason - it stands for Complex Instruction Set Computer), and with parts manufactured in the 1990's and 2000's still available to buy new today - and if not, you could always raid the used parts bin, in fact some people do - and make a competition out of it.
(Notice - details are correct at the time of publication)
There are three kits in particular that have interested me in recent times, these are:
1. The RC2014
Winner of the Retro Challenge 2014, this kit is built around a backplane, with small module boards for the CPU, ROM, RAM, and Serial communications. The advantage is, that you can build it up piece by piece, and so are not confronted by a daunting number of connections on an expensive board, that might be wrecked by a couple of mistakes.
The modules are available to buy separately either as bare PCB's or kits of parts, and the creator of the RC2014 is continuing to add new modules, as could the owner in the spirit of the creativity of the early microcomputer scene. I've been trying to build one slowly myself. The only negative comment I will make is that Tindie, the shopping service on which the RC2014 is sold - throws up some warnings from security software, and some may find that disconcerting. The seller does often pop up on eBay.co.uk as well, selling the same products.
The RC2014 is available on Tindie from seller Semachthemonkey (no relation to Cap'n Goode), with prices starting from £16.11GBP at www.tindie.com/products/Semachthemonkey/rc2014-homebrew-z80-computer-kit/
2.The Harlequin
Before appearing, and then disappearing, as part of a team working on a well known crowd-funded plug and play, Chris Smith was well known for having reversed engineered the ULA (Uncommitted Logic Array) in the ZX Spectrum, the one custom chip - similar to a CPLD - that assisted the Z80A inside Sinclair Research's microcomputer in displaying video, loading and saving, and other tasks. The research was published in a book, entitled 'The ZX Spectrum ULA - Designing a Microcomputer'.
From that research, and further work by the Spectrum community, the Harlequin Superfo was born - available as a 48k or 128k model, the board implements the ZX Spectrum ULA as ordinary logic IC's. This is an interesting, if daunting project (with it's many components - in 1981 theZX81 had just 3 chips), in a world where original ZX Spectrums are failing, being cannibalised for parts to fix other Spectrums, being modded, and generally shrinking in number - as the Harlequin fits comfortably inside a ZX Spectrum + casing (the one with the QL-style upgrade keyboard, and is a fully featured clone complete with all aspects and abilities of the original micro.
The Harlequin can be bought as a bare PCB at £24.99, or a kit of parts costing £84.99, and is available in the webshop at www.bytedelight.com
3.The Z80 Membership Card
Available from the US via international postage, the Z80 Membership Card is a pocket sized microcomputer which the creator, Lee A.Hart, describes as being a bit like an Arduino, BASIC Stamp, or other such development board.
It is comprised of two fully developed boards, handling central processing operations and serial communication, and an optional third proto-board for adding to the design yourself. There is a built in Hexadecimal keyboard and full QWERTY control through RS232 serial.
There is also a fictional story accompanying the development of the Membership Card, featuring characters with almost familiar names, such as Gil Bates, who has been inspired to design his own computer by the recent arrival of the Altair 8800 on the electronics scene. That computer, of course - is the Membership Card, small enough to fit in an Altoids tin. I had to do an internet search to find out what Altoids are - it turns out they are a type of breath mint.
The Z80 Membership Card is priced at $19USD plus $10 for international shipping, or $80+$15 international shipping available from www.sunrise-ev.com/z80.htm
Disclaimer: Please observe that I cannot hold accept any responsibility for any results of you buying or trying to build these kits.
Thanks for reading! Stephen