MK14

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Microcomputer Kit 14
Sinclair - Science of Cambridge MK14.jpg
MK14 (foreground) with modern reproductions behind
Also known as MK14
Manufacturer Science of Cambridge
Type computer kit
Release date 1977; 41 years ago (1977)[1]
Introductory price UK£39.95
Units sold 15–15,000[2] (another source states 50,000[3])
CPU National Semiconductor SC/MP (INS8060)
Memory 256 bytes of RAM (expandable to 640 bytes)
Display 8 or 9 red light-emitting diode (LED) seven segment display
Input 20 key keyboard

The Microcomputer Kit 14, or MK14 was a computer kit sold by Science of Cambridge of the United Kingdom, first introduced in 1977 for UK£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]

History[edit]

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 design for free.[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]

Specification[edit]

The computer is based around National Semiconductor's SC/MP CPU (INS8060) and shipped with 256 bytes of random access memory (RAM) 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. 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 home-brew computer magazines such as Personal Computer World, and Practical Electronics carried details of user modifications.

Notes[edit]

See also[edit]

External links[edit]