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1980s Computers Explanation of terms

The Microcomputer Kit 14

Microcomputer Kit 14


Science of Cambridge (UK)
(Later became Sinclair Research)


Microcomputer Kit 14 (MK14)

Date Launched

June 1978



Microprocessor type

National Semiconductor SC/MP 2 @ 4.4MHz
The 'Simple Cost effective Micro Processor' was designed primarily as a microcontroller and ran at about 100,000 instructions per second.

ROM size

512 bytes

Standard RAM

256 bytes
(Note that is 256 bytes, not kilobytes.)

Maximum RAM

640 bytes on-board.
Up to 2176 bytes was possible with minor modifications.

Keyboard type

20 key touch sensitive membrane, using conductive rubber to bridge P.C.B. tracks, and providing hexadecimal 0-9 and A-F plus Go, Mem, Abort and Term.
This keyboard was unreliable and from version 4 of the kit, individual mechanical pushbuttons were substituted.

Supplied language

Machine code loader

Text resolution

8 hexadecimal digits using a seven segment LED calculator display.
A 32 x 16 character television display was an optional extra.

Graphics resolution

64 x 64 pixels with optional VDU display adaptor

Colours available

Red LED. Monochrome with VDU adaptor.

Example Screenshot

MK14 LED display
The type of display produced by an 'animated graphics' program on the unexpanded MK14. Less was expected of computer games in those days.


None except by connecting a speaker to the output port and rapidly toggling the bit.

Cassette load speed

Optional cassette interface operated at 40 baud.

Dimensions (mm)
Weight (grams)

115 x 255 x 30 approx.
Not known

Special features

Supplied as a build-it-yourself kit of parts, without a case.
Contained the bare minimum of components to make a working computer.

Good points

The cheapest 'computer' available.
The SC/MP microprocessor was easy to learn to program.
A PROM programmer was available from Science of Cambridge. The idea was that you could write a program to perform a specific task (Science of Cambridge's example was a model railway controller), transfer it to PROM and use this to replace the MK14's standard PROM. You then had a custom-designed microcontroller at a low price.

Bad points

There was not a lot you could do with 256 bytes of memory and an 8 digit display.
There were delays of 3 months or so in fulfilling orders.

How successful?

Around 15,000 were sold, a considerable number for the early days of computing.


The MK14 was Clive Sinclair's first computer and although its specification was nowhere near the contemporary PET and Apple, it was just about a programmable computer. If the MK14 had not sold well there might never have been a ZX80, ZX81 and ZX Spectrum, or Acorn's range of computers. (Chris Curry, the co-founder of Acorn, worked for Science of Cambridge in the late 1970's.)

The MK14 was only really suitable for learning the basics of machine language programming of microprocessors, which most people had not even heard of in 1978. In typical Sinclair style though the magazine advertisements made much of its possibilities, even claiming that it 'handles complex games'. (In 256 bytes?)

Unassembled MK14 kits are now very rare and worth several hundred pounds to collectors.

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