Memotech MTX

The Memotech MTX500, MTX512[4] and RS128[2] are a series of Zilog Z80A processor-based home computers released by Memotech in 1983[5] and 1984.[6]

Memotech MTX
Memotech MTX500.jpg
Memotech MTX500
Release date1983; 39 years ago (1983)
Introductory price£275 (equivalent to £987 in 2021) (MTX 500),
£315(equivalent to £1,131 in 2021) (MTX 512),
C$1,000 (equivalent to $2,261 in 2020) (MTX 512) with C$1,700 (equivalent to $3,843 in 2020) for "New Word" software and an 80-cps printer.[1],
£399 (equivalent to £1,364 in 2021) (RS 128)[2]
Operating systemCP/M[3];
BASIC, LOGO, NODDY (MTX 500, 512);[3]
MTX BASIC, NODDY, Assembler (RS 128)[2]
CPUZilog Z80A @ 4MHz[3]
Memory32KB (MTX 500), 64KB (MTX 512)[3] or 128KB (RS 128)[2]
StorageCassette, 5.25" floppy disk[3]
DisplayComposite BNC, RF RCA
GraphicsTMS9918 or 9928[3]
SoundSN76489A[3] 3.5mm phono
Controller input2×DE-9
ConnectivityRS-232 (2), Parallel (34-pin Centronics type header), edge connector (left), bus interface connector (bottom)
Dimensions48.6 x 20.3 x 5.7 cm[3]
Mass2.6 Kg[3]

The MTX500 had 32 KB of RAM, the MTX512 had 64KB,[7] and the RS128 had 128KB. Although the Z80A could only address a maximum of 64KB at a time, the MTX and RS128's extra memory, up to a maximum of 768KB, was accessible through the technique of page switching. All models had 24KB of ROM accessible in the first 16KB of address space. The extra 8KB of ROM was available through page switching. The ROM could be switched out entirely, allowing the full 16-bit address space to be used for RAM.

The computers featured an all-aluminum case and full-size keyboard with real keys (unlike the chiclet keyboard used on the Sinclair ZX Spectrum).[5] In addition to the standard (for the time) BASIC language interpreter (with rudimentary windowing support and LOGO commands support[8]), it included some other software: an assembler, the Panel disassembler/debugger and the Noddy graphic language aimed at children[5])

This series also featured support for plug-in ROM cartridges (a little like the BBC Micro). The most popular of these was the ISO Pascal language from HiSoft which was much faster than interpreted BASIC. A considerable addition to any Memotech system was the hugely expensive FDX system which added 5.25" floppy disk drives, Winchester hard disks and CP/M 2.2 operating system. A Memotech-badged CGA monitor was also made available around the time of the FDX launch.


In 1984, the Norwegian company Norbit Elektronikk Norge A/S run by A. S. Fiko developed a complete Input/Output (I/O) control system with 4× 16-bits by using the blue Memotech 8-bit Dual in-line package DIL socket for I/O controls. The socket was located on the computer motherboard. Norbit Elektronikk used their Super ToolBox system and was able to use 16-bits by adding two data blocks of 8 bits at the same time. Digital I/O ports, Analog-to-digital converter and Digital-to-analog converter with all kind of sensor systems for robotics and controls were developed. The control system was designed for the same aluminum casing as the main MTX512 unit.

In 1984/85 Memotech was working on a huge project to deliver the CP/M-based MTX512 together with the FDX and the control unit from Norbit Elektronikk to 64,000 schools in the USSR[9] with the potentials to sell about 200,000 units. The USSR was at that time under embargo by the United States, and companies were not allowed to deliver the new IBM Personal Computer with MS-DOS to USSR. CP/M computers were not included in the Soviet embargo blockage and Memotech's MTX512 was therefore a good option.

Memotech went into receivership in 1985. A contributing factor, beyond the poor commercial success of the MTX, was the substantial investment Memotech made in preparing the MTX512 for the Soviet deal. This required a red brushed aluminum case instead of the black (made at a factory in the Netherlands), Russian BASIC, Russian character encoding, Russian keyboard and Russian documentation. Memotech worked with a professor at University of Oxford for the internationalization.

The Soviet government was also evaluating computer systems from other home computer manufacturers. Memotech was relying on the British government for funding the project, but ultimately, they only received about £1m and did not receive the full funding required. As a result, Memotech required cash payments from the USSR prior to supplying the 64,000 computers. The Soviets decided against this cash deal and instead agreed to acquire MSX computers from Yamaha (another later big deal was with Daewoo) with bartering mainly in steel and oil. Only a few thousand MSX computers were supplied to USSR schools and other educational institutions [10][11] before the deal went dead. The main reason was the USSR thought that MSX was the new Microsoft Operating system.

Since Memotech lost the deal to the USSR,[9] and they had invested all their money in the project, money that was borrowed from the banks, plus the £1m funding from the UK government, Memotech went bankrupt. Some of the Memotech inventions still lived on, as several employees took some of Memotech's new video editing systems for televisions back to the USA. As a result of Memotech's bankruptcy, the UK government stopped funding to all computer manufacturers in the UK at that time, including Sinclair, Acorn and Apricot.

Control systems from Norbit Elektronikk are in 2019 still sold under the registered brand name of MISOLIMA.


  • CPU: Zilog Z80 A @ 4MHz[3]
  • Video: TM9918 or 9928 (256 x 192 resolution, 16 colors)[3]
  • Sound: SN76489A (3 voices + pink noise, 6 octaves)[3]
  • RAM: 32 KB (MTX-500) / 64 to 512 KB (MTX-512)[3]
  • OS: CP/M[3]

In popular cultureEdit

The MTX512 made a minor cinematic appearance in the film Weird Science as the computer the two lead male characters use to hack into the Pentagon mainframe.[12]


  1. ^ [1], Advertisement in Computing Now! June 1984
  2. ^ a b c d "OLD-COMPUTERS.COM : The Museum".
  3. ^ a b c d e f g h i j k l m n "OLD-COMPUTERS.COM : The Museum".
  4. ^ Advertisement: A world apart from the ordinary: Introducing the MT512, InfoWorld, 18 Jun 1984, Page 24, ...16 color, 256 x 192...
  5. ^ a b c "Evening Times". Evening Times – via Google Books.
  6. ^ "Popular Computing". McGraw-Hill. August 16, 1984 – via Google Books.
  7. ^ Bits & Bytes, By William J. Hawkins, Popular Science, Jan 1984, Page 140, New Computers:..Memotech's MTX-512 desk-top computer...The Z80 system comes with 80K of RAM, BASIC(with LOGO commands for graphics), and is CP/M compatible. Starting price $595.
  8. ^ Corporation, Bonnier (January 16, 1984). "Popular Science". Bonnier Corporation – via Google Books.
  9. ^ a b Popular Computing Weekly To Russia with love
  10. ^ USSR UK firms let-down as USSR goes MSX
  11. ^ MEMOTECH to USSR. The Sovjet deal
  12. ^ Memotech MTX 512, Starring the Computer

External linksEdit