ZX80 | 1980

ZX80

 The Sinclair ZX80 is a home computer launched on January 29, 1980, by Science of Cambridge Ltd. (later known as Sinclair Research). It is notable for being one of the first computers available in the United Kingdom for less than a hundred pounds. It was available in kit form for £79.95, where purchasers had to assemble and solder it together, and as a ready-built version for £99.95.

The ZX80 was advertised as the first personal computer for under £100 and received praise for its value and documentation. However, it faced criticism for screen blanking during program execution, small RAM size, and the keyboard design. It became very popular immediately, and for a time there was a waiting list of several months for either version of the machine.

Name

The ZX80 was named after the Z80 processor, with the 'X' representing the "mystery ingredient."

Hardware

Internally, the machine was designed by Jim Westwood around a Z80 central processing unit with a clock speed of 3.25 MHz, and it was equipped with 1 KB of static RAM and 4 KB of read-only memory (ROM). It had no sound output.

The ZX80 was designed using standard TTL chips, with the only proprietary technology being its firmware. The machine was housed in a small white plastic case, with a one-piece blue membrane keyboard on the front. It had problems with durability, reliability, and overheating, and the black stripes visible on the top rear of the case were just decorative, not ventilation slots.

The video output was black-and-white and character-based. However, the ZX80’s character set included simple block-based graphics, allowing basic graphics to be created with some effort. One advantage of using monochrome video was that color broadcast standards (e.g., PAL, SECAM) weren't an issue when the machine was sold outside the UK.

The display was output to a household television via an RF connection, 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 the video signal. Unlike the later ZX81, the ZX80 could only generate a picture when it was idle, and during program execution, the display would blank out. This could be overcome only by very clever machine code techniques.

Firmware

The 4 KB ROM contained the Sinclair BASIC programming language, editor, and operating system. BASIC commands were not typed out directly but were selected using keys that functioned like a programmable graphing calculator.

Expansion

Other than the built-in cassette and video ports, the ZX80 featured an expansion slot at the rear of the case, providing a bus connector on the motherboard. This encouraged a small industry of expansion devices, including memory packs, printers, and even floppy drives. The original ZX80 RAM pack offered 1 KB, 2 KB, or 3 KB of static RAM, with later models providing 16 KB of dynamic RAM.

A ZX81-style 8 KB ROM upgrade was available for the ZX80, which, when installed, made the ZX80 function similarly to a ZX81, although it still ran slower due to hardware differences.

Versions

The UK version of the machine was the standard, with only minimal changes made for other markets, such as adjusting the video output frequency. Notably, the keyboard and character set included British symbols, such as NEWLINE instead of Enter and RUBOUT instead of Backspace.

Reception

The ZX80 was widely advertised as the first personal computer for under £100. Kilobaud Microcomputing praised the preassembled version but noted that the screen flickering was annoying, though it indicated the computer was functioning correctly. BYTE called the ZX80 "remarkable," highlighting its real-time BASIC syntax checking but criticizing its screen blanking, small RAM, inadequate built-in BASIC, and keyboard.

The ZX80 sold around 50,000 units, significantly contributing to the UK's leadership in home computer ownership during the 1980s. Because of its simplistic design and overheating issues, surviving ZX80s in good condition are now sought after by collectors and can fetch high prices.

Clones

There were ZX80 clones, such as the MicroAce, and from Brazil, the Nova Eletrônica/Prológica NE-Z80 and the Microdigital TK80.