ZX Spectrum (Retro)

Science of Cambridge MK-14

The Microcomputer Kit 14 (MK 14) was Sinclair's (at that time called “Science of Cambridge”) first computer introduced in 1977 for UK £39.95. Based on the National Semiconductor SC/MP processor, the MK 14's capabilities were minimal by today's standards - modern digital watches are considerably more powerful!

Despite the MK 14's severe limitations, it was one of the most important British computers ever produced. The MK14 eventually sold over 50,000 units. Its success in finding a previously untapped market was not lost on either Sinclair or his employees, notably Chris Curry, soon to break away and establish Acorn. Without the MK 14, there probably would never have been a ZX81, Spectrum, BBC Micro or Archimedes, and the British computer scene would have been very different.

The MK14 specification:
1/2k ROM Monitor
256 bytes RAM (expandable to 640 bytes on board and 2170 bytes total)
8 (or 9) Red LED seven segment display.
20 key keyboard and reset switch
Optional 16 I/O lines available by adding a IC
No sound card (design provided)
No backing store (cassette and PROM storage an optional extra)
Optional VDU supporting 32x16 text or 64x64 graphics
source: http://www.computinghistory.org.uk/det/8095/science-of-cambridge-mk14/

Sinclair ZX80

Developer: Science of Cambridge (renamed to Sinclair Computers Ltd in November in 1979)
Type: Home Computer
Operating system: Sinclair BASIC
CPU: Z80 @ 3.25 MHz (most machines used the NEC μPD780C-1 equivalent)
Memory: 4K ROM, 1K RAM (externally expandable to 16K)
Display: 24 lines x 32 character text display Monochrome only
Sound: None, I/O Z80 bus, 250 baud cassette interface, RF television out
Storage: External cassette recorder
Successor: ZX81
Very slow program execution - no video chips, the CPU performs all of the computer functions
The keyboard is a membrane-type, a flat plastic surface which is difficult to use and wears-out rather quickly.
There was an upgrade kit to the ZX81 as can be seen in the last photo.

Sinclair ZX81

Developer: Sinclair Research
Manufacturer: Timex Corporation
Release date: 5 March 1981
Discontinued: 1984
Type: Home Computer
Predecessor: ZX80
Successor: ZX Spectrum
Operating system: Sinclair BASIC
CPU: Z80 at 3.25 MHz
Storage capacity: External cassette tape recorder at 250 baud
Memory: 1 KB (64 KB max. 56 KB usable)
Display: Monochrome display on UHF television
Graphics: 24 lines x 32 characters or 64 x 48 pixels graphics mode
The computer is composed of only four IC chips, and there are no video chips or co-processors. The CPU has to perform all of the tasks that are required of a computer, which means it executes the BASIC program and updates the screen at the same time, slowing the program speed. The fix? Don't update the display as often - the SLOW and FAST commands determine the video display rate. The FAST command allows the program to run 4X faster, but then the display gets jerky.
Other models:
Timex Sinclair 1000, 1982, sold by Timex in USA
Timex Sinclair 1500, 1983, sold by Timex in USA, stop-gap between the TS 1000 and the forthcoming American version of the Spectrum, the TS 2000 (never released). It was a ZX81 with an internally housed 16K RAM expansion module, in a black and silver Spectrum-style box with the familiar "dead flesh" rubber keyboard. The updating of the ZX81 design was an attempt to counter the two biggest drawbacks of the TS 1000, namely the touch-sensitive keyboard and the minuscule 1K of memory. The machine failed dismally: no matter how much it was dressed up, it was still a ZX81, with most of that machine's limitations still intact.

Sinclair ZX Spectrum (16K/48K) All Issues

Developer: Sinclair Research
Release date: April 23, 1982
Discontinued: 1992
Type: Home Computer
Operating system: Sinclair BASIC
CPU: Z80 @ 3.5 MHz and equivalent
Memory: 16 KB / 48 KB
Display: 32 x 22 character text display 256 x 192 pixel resolution 8 colours
Sound: 1 channel, 5 octaves
I/O Z80 bus, tape, RF television
Storage: External tape recorder or microdrives
Predecessor: ZX81

Sinclair ZX Spectrum (16K/48K) - Issue 1

Developer: Sinclair Research
Release date: April 23, 1982
Discontinued: 1992
Type: Home Computer
Operating system: Sinclair BASIC
CPU: Z80 @ 3.5 MHz and equivalent
Memory: 16 KB / 48 KB
Display: 32 x 22 character text display 256 x 192 pixel resolution 8 colours
Sound: 1 channel, 5 octaves
I/O Z80 bus, tape, RF television
Storage: External tape recorder or microdrives
Predecessor: ZX81

Sinclair ZX Spectrum (16K/48K) - Issue 2-6

Developer Sinclair Research Release date April 23, 1982 Discontinued 1992 Type Home Computer Operating system Sinclair BASIC CPU Z80 @ 3.5 MHz and equivalent Memory 16 KB / 48 KB Display 32 x 22 character text display 256 x 192 pixel resolution 8 colours Sound 1 channel, 5 octaves I/O Z80 bus, tape, RF television Storage External tape recorder or microdrives Predecessor ZX81 Successor Sinclair QL

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