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Microcomputer Kit 14
Sinclair - Science of Cambridge MK14.jpg
MK14 (foreground) with modern reproductions behind
Also known asMK14
ManufacturerScience of Cambridge
Typecomputer kit
Release date1977; 45 years ago (1977)[1]
Introductory priceGBP 39.95
Units sold15,000[2] (another source states 50,000[3])
CPUNational Semiconductor SC/MP (INS8060)
Memory256 bytes of RAM (expandable to 640 bytes) + 512 bytes of ROM
Display8 or 9 red light-emitting diode (LED) seven segment display
Input20 key keyboard

The MK14 (Microcomputer Kit 14) was a computer kit sold by Science of Cambridge of the United Kingdom, first introduced in 1977 for £39.95.[1] The price was very low for a complete computer system at the time,[1][4] and Science of Cambridge eventually sold over fifteen thousand kits.[2]


Prototype of the MK14

In 1977, Ian Williamson approached Clive Sinclair and Chris Curry with a computer design based around the National Semiconductor SC/MP processor. Sinclair and Curry both liked the idea and saw the potential of making a low cost microprocessor system available to the hobbyist market. Initially it was planned to market a kit based on the Williamson design. However, after National Semiconductor had been contacted regarding a bulk purchase of the SC/MP processor Sinclair and Curry decided to use the chip manufacturer's own design. This design used all National Semiconductor chips and the company allowed the use of its designs, the SC/MP Introkit and Keyboard Kit, for free. The National Semiconductor SCMPKB Monitor code was included. [2][4]

To keep costs low a membrane keypad was used. The size of the initial batch was two thousand. The company sold between fifteen and fifty thousand in total.[2]


The computer is based around National Semiconductor's SC/MP CPU (INS8060) and shipped with 256 bytes of random access memory (RAM) and 512 bytes of read only memory (ROM) as standard. It used an eight or nine red light-emitting diode (LED) seven segment display, there was also optional VDU supporting 32×16 text or 64×64 graphics.[citation needed] Input and output was a 20-key keyboard and reset switch. Cassette-based and PROM storage were optional extras; a sound card was not included but a design for one was provided.

The on-board RAM could be increased in two ways; by the addition of an INS8154N RAM/IO chip providing an additional 128 bytes of RAM along with 16 I/O lines, and also a further 256 bytes by adding two 256 × 4 bit RAM chips giving a maximum of 640 bytes on board. These memory spaces were not contiguous in the memory map. It was possible to connect off-board RAM giving a 2170 bytes total.[citation needed]

The MK14 could address up to 64 KB of memory space by adding a few chips (the NADS address strobe indicated when the most significant four bits of address were available to be captured by an external latch); many pioneering homebrew computer magazines such as Personal Computer World, and Practical Electronics carried details of user modifications.

See also[edit]


  1. ^ a b c "Planet Sinclair: Computers: MK 14: Articles: PE 5/79".
  2. ^ a b c d "Ian Williamson: The engineer who gave Sinclair his first micro".
  3. ^ Sinclair, Planet. "Planet Sinclair: Computers: MK 14".
  4. ^ a b Computerphile (15 November 2017). "1978's Raspberry Pi (MK14) - Computerphile". Archived from the original on 2021-12-22 – via YouTube.

External links[edit]