The MK-14 was the first computer made by the Sinclair company (at the time called Science of Cambridge because the Sinclair name was used by another company).
The MK-14 was a training board sold in kit form for £39.95 and featuring a National Semiconductor SC/MP 8-bit processor, 256 bytes of RAM, 512 bytes of ROM holding a monitor, calculator keyboard and display, and some I/O ports.
In fact, Clive Sinclair was not very enthusiastic about a personal computer project. The MK-14 project was thus managed by Chris Curry and produced by National Semiconductor. As the system was five times cheaper than its closest competitor, the Compukit UK-101, about 20,000 MK-14 boards were sold in the U.K.
Chris Curry, who believed much more than Clive Sinclair in the future of such computers, left the company in 1978, founded Acorn Computers with Herman Hauser and built its fist computer kit, the System 1. A few months later, Clive Sinclair decided that computers were a good way to raise money and started a new project: a complete computer for less than £100.
Meantime, the MK-14 grew into a modular system and several additional cards allowed expansion of the system: cassette interface, text and graphics video module and Eprom programmer. 128 and 256 bytes RAM expansion chips could also be added up to a total of 640 bytes. Yes...640 BYTES...
The version pictured here is an issue 4 with a better mechanical keyboard than the 'sensitive' one of the earlier versions, as well as optional RAM and I/O chips. At least 5 issues were sold. The issue 5 featured additional I/O ports.
If the MK-14 had not been launched, Clive Sinclair probably wouldn't have thought of his ZX-80 so soon, and the global personal computer scene would have been very different.
David Rayner adds:
The Keyboard was unreliable I bought a separate keyboard. There was no storage so every program had to typed in machine code every time. (I never had the tape interface).
The first test program was jmp 0000 (3 bytes). There was a shoot the duck game (a character flying acroos the calculator style display). By connecting a speaker you play "music". It was actually quite fun.
Mark Dodd reports to us:
We used these things with a ROM burner in an Australian college for our Microprocessor training.
The smarter ones in the classes wrote programs that rewrote themselves as they went.