The
Sinclair ZX80 was a
home computerHome computer was a class of personal computer entering the market in 1977 and becoming increasingly common during the 1980s. They were marketed to consumers as accessible personal computers, more capable than video game consoles...
brought to market in 1980 by Science of Cambridge Ltd., until 1977 known as Sinclair Instrument and later to be better known as Sinclair Research. It was notable for being the first computer (unless you consider the
MK14The 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. The MK14 eventually sold over 50,000 units. It used a National Semiconductor SC/MP CPU , 256 bytes of random access memory which was directly expandable...
) available in the
United KingdomThe United Kingdom of Great Britain and Northern Ireland is a sovereign state located off the northwestern coast of continental Europe. It is an island country, spanning an archipelago including Great Britain, the northeastern part of Ireland, and many small islands...
for less than a hundred
poundsThe pound sterling , often simply called the pound, is the currency of the United Kingdom, its Crown dependencies and the British Overseas Territories of South Georgia and the South Sandwich Islands and British Antarctic Territory...
(£99.95). It was available in kit form, where purchasers had to assemble and solder it together, and as a ready-built version at a slightly higher cost for those without the skill or inclination to build their own unit.
The
Sinclair ZX80 was a
home computerHome computer was a class of personal computer entering the market in 1977 and becoming increasingly common during the 1980s. They were marketed to consumers as accessible personal computers, more capable than video game consoles...
brought to market in 1980 by Science of Cambridge Ltd., until 1977 known as Sinclair Instrument and later to be better known as Sinclair Research. It was notable for being the first computer (unless you consider the
MK14The 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. The MK14 eventually sold over 50,000 units. It used a National Semiconductor SC/MP CPU , 256 bytes of random access memory which was directly expandable...
) available in the
United KingdomThe United Kingdom of Great Britain and Northern Ireland is a sovereign state located off the northwestern coast of continental Europe. It is an island country, spanning an archipelago including Great Britain, the northeastern part of Ireland, and many small islands...
for less than a hundred
poundsThe pound sterling , often simply called the pound, is the currency of the United Kingdom, its Crown dependencies and the British Overseas Territories of South Georgia and the South Sandwich Islands and British Antarctic Territory...
(£99.95). It was available in kit form, where purchasers had to assemble and solder it together, and as a ready-built version at a slightly higher cost for those without the skill or inclination to build their own unit. The ZX80 was very popular straight away, and for some time there was a waiting list of several months for either version of the machine.
Description
The machine was designed by
Jim WestwoodJim Westwood was the chief engineer at Sinclair Research Ltd in the 1980s, starting at the company in 1963. Westwood was the technical mastermind behind many of Sinclair's products and worked there for more than twenty years...
around a Z80
central processing unitThe Central Processing Unit or processor is the portion of a computer system that carries out the instructions of a computer program, and is the primary element carrying out the computer's functions. This term has been in use in the computer industry at least since the early 1960s...
with a clock speed of 3.25 MHz, and was equipped with 1
KBThe kilobyte is a unit of digital information storage equal to either 1,000 bytes or 1,024 bytes , depending on context....
of static RAM and 4 KB of
read-only memoryRead-only memory is a class of storage media used in computers and other electronic devices. Because data stored in ROM cannot be modified , it is mainly used to distribute firmware .In its strictest sense, ROM...
containing the
Sinclair BASICSinclair BASIC is a dialect of the BASIC programming language used in the 8-bit home computers from Sinclair Research and Timex Sinclair...
programming languageA programming language is an artificial language designed to express computations that can be performed by a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine, to express algorithms precisely, or as a mode of human...
, editor, and
operating systemAn operating system is an interface between hardware and user which is responsible for the management and coordination of activities and the sharing of the resources of the computer that acts as a host for computing applications run on the machine. As a host, one of the purposes of an operating...
. BASIC commands were not entered by typing them out but were instead selected somewhat similarly to on a scientific calculator - each key had a few different functions selected by both context and modes as well as with the shift key.
Display was over an RF connection to a household
televisionTelevision is a widely used telecommunication medium for transmitting and receiving moving images, either monochromatic or color, usually accompanied by sound. "Television" may also refer specifically to a television set, television programming or television transmission...
, and simple offline program storage was possible using a cassette recorder. The video display generator of the ZX80 used minimal hardware plus a combination of software to generate a video signal. This was an idea that was popularised by
Don LancasterDonald E. Lancaster is a prolific author, inventor, and microcomputer pioneer best known for his magazine columns. He is also known for his "TV Typewriter" dumb terminal project, his book on technical entrepreneurship The Incredible Secret Money Machine, and his work on and advocacy of early...
in his 1978 book The TV Cheap Video Cookbook and his "
TV TypewriterThe TV Typewriter was a video terminal that could display 2 pages of 16 lines of 32 upper case characters on a standard television set. The Don Lancaster design appeared on the cover of Radio-Electronics magazine in September 1973. The magazine included a 6 page description of the design but...
". As a result of this approach the ZX80 could only generate a picture when it was idle, i.e. waiting for a key to be pressed. When running a BASIC program, or even when pressing a key for any input, the display would, therefore, black out momentarily while the processor was busy. This made moving graphics difficult since the program had to introduce a pause for input to display the next change in graphical output. The later
ZX81The Sinclair ZX81 was a home computer released in 1981 by Sinclair Research. It was the follow-up to the Sinclair ZX80.The machine's distinctive appearance was the work of industrial designer Rick Dickinson. Video output, as in the ZX80, was to a television set, and saving and loading programs was...
improved on this somewhat because it could run in a "slow" mode while creating a video signal, or in a "fast" mode without generating a video signal (typically used for lengthy calculations). Another issue was that the main RAM was used to store the screen display, with the result that the available screen size would gradually decrease as the size of a program increased - with 1KB RAM, running a 990 byte program would result in only one row of characters being visible on the screen.
A ZX81 8 KB
ROMRead-only memory is a class of storage media used in computers and other electronic devices. Because data stored in ROM cannot be modified , it is mainly used to distribute firmware .In its strictest sense, ROM...
was available to upgrade the ZX80 at a cost of around 20% of a real ZX81. It came with a thin keyboard overlay and a ZX81 manual. Simply taking off the top cover of the ZX80 and prying the old ROM from its socket and carefully inserting the new ROM and adding the keyboard overlay, the ZX80 would now function almost identically to the proper ZX81 - except for SLOW mode, due to the differences in hardware between the two models. The process was easily reversed to get the ZX80 back to its old self.
Sinclair also produced RAM expansion packs for the ZX80; the original ZX80 RAM Pack held either 1, 2 or 3 KB of static RAM, a later model held 16 KB, using dynamic RAM chips (DRAM).
The machine was mounted in a tiny white plastic case, with a one-piece blue
membrane keyboardA membrane keyboard is a computer keyboard whose "keys" are not separate, moving parts, as with the majority of other keyboards, but rather are pressure pads that have only outlines and symbols printed on a flat, flexible surface...
on the front; it owed its distinctive appearance to industrial designer
Rick DickinsonRick Dickinson was the in-house industrial designer of Sinclair Research Ltd. In 1986, he founded Dickinson Associates, an industrial design consultancy....
. There were problems with durability, reliability and over-heating.
Reception
Sales of the ZX80 reached about 50,000 — an unheard of number for the day which contributed significantly to the UK leading the world in home computer ownership through the 1980s. Owing to the unsophisticated design and the tendency for the units to overheat, surviving machines in good condition are quite uncommon and can fetch high prices by collectors.
Hardware
The ZX80 was designed around readily available TTL chips; the only proprietary technology was the firmware. While the successor ZX81 used a semi-custom chip (a ULA or Uncommitted Logic Array), this merely combined the functions of the earlier hardware onto a single chip — the hardware and system programs (except the BASIC versions) were very similar, with the only significant difference being the
NMIA non-maskable interrupt is a computer processor interrupt that cannot be ignored by standard interrupt masking techniques in the system. It is typically used to signal attention for non-recoverable hardware errors...
-generator necessary for slow mode in the ZX81. (See ZX81 for technical details.) Both computers can be made by hobbyists using commercially available discrete logic chips or FPGAs.
Clones
There were also unauthorised clones of the ZX80, namely the
MicroAceThe MicroAce was an unlicensed clone of the Sinclair ZX80, manufactured by the eponymous MicroAce of Santa Ana, California. The MicroAce came with an option to expand the internal random access memory to 2K, but had an identical copy of the ROM. The company was sued by Sinclair Research, who were...
(produced in the USA) , and from
BrazilBrazil , officially the Federative Republic of Brazil , is a country in South America. It is the fifth largest country by geographical area, occupying nearly half of South America, the fifth most populous country, and the fourth most populous democracy in the world. Bounded by the Atlantic Ocean...
the NOVA Electônica/Prológica NE-Z80 and the Microdigital TK82
External links