Thomson MO5


The Thomson MO5 is a home computer introduced in France in June 1984[2] to compete against systems such as the ZX Spectrum and Commodore 64. At the same time, Thomson also released the up-market Thomson TO7/70 machine.

Thomson MO5.jpg
Thomson MO5
ManufacturerThomson SA
Release date1984; 38 years ago (1984)
Discontinued1986; 36 years ago (1986)
MediaCassette tape, Cartridges
Operating systemMO5 BASIC 1.0
CPUMotorola 6809E @ 1 MHz
Memory32 KB RAM, 16 KB VRAM
Display320x240, 8 colours with 2 saturation variations, 2 colours per 8x1 pixel area
GraphicsEFGJ03L gate array[1]
Sound1-bit square wave
InputKeyboard, Lightpen
Controller inputJoystick
ConnectivityExpansion port
SuccessorThomson MO6
Related articlesThomson TO7/70

The MO5 was not sold in vast quantities outside France and was largely discontinued in favour of the improved Thomson MO6 in 1986. MO5s were used as educational tools in French schools for a period.[3] The computer boots directly to the built-in Microsoft BASIC interpreter (MO5 Basic 1.0).[2]


The Thomson MO5 runs on a Motorola 6809E processor clocked at 1 MHz and features 48 KB of RAM (16 KB used as video memory, 32KB as free user RAM) and 16KB of ROM (4KB for the monitor and 12KB for the BASIC interpreter).[4]

Graphics were generated by a EFGJ03L (or MA4Q-1200) gate array[1] capable of 40×25 text display and a resolution of 320 x 200 pixels with 16 colours (limited by 8x1 pixel colour attribute areas).[3][4]. The colour palette is 4-bit RGBI, with 8 basic RGB colours and a intensity bit (called P for "Pastel") that controlled saturation ("saturated" or "pastel").[5][6] In memory, the bit order was PBGR. The desaturated colours were obtained by mixing of the original RGB components within the video hardware. This is done by a PROM circuit, where a two bit mask controls colour mixing ratios of 0%, 33%, 66% and 100% of the saturated hue. [5] This approach allows the display of Orange instead of "desaturated white", and Gray instead of "desaturated black".

According to the values specified on the computer's technical manual (“Manuel Technique du MO5”,[5] p. 11-19), the hardware palette was:[6]

Thomson MO5 Hardware Palette[6]
Memory bits


PROM bit mask

B2B1 G2G1 R2R1

Name Memory bits


PROM bit mask

B2B1 G2G1 R2R1

0000 00 00 00 Black 1000 10 10 10 Gray
0001 01 01 11 Red 1001 10 10 11 Rose
0010 00 11 00 Green 1010 10 11 10 Light Green
0011 00 11 11 Yellow 1011 10 11 11 Light Yellow
0100 11 01 01 Blue 1100 11 10 01 Light Blue
0101 11 00 11 Magenta 1101 11 10 11 Parma Pink
0110 11 11 01 Cyan 1110 11 11 10 Light Cyan
0111 11 11 11 White 1111 01 10 11 Orange

Displayed colors are only approximate due to different transfer and color spaces used on web pages (sRGB) and analog video (BT.601)

Video RAM was 16KB. As common on home computers designed to be connected to an ordinary TV screen, the 320 x 200 pixels active area doesn't cover the entire screen, and is surrounded by a border.[5] The video output is RGB on a SCART connector, with the refresh rate being 625-line compatible 50Hz.[4]

Audio is limited to 1-bit square wave tones, outputted via the TV using the SCART connector. The tape player's output is also routed to the computer's sound output.[4]

The keyboard has 58 keys and includes a reset button.

The machine used cassette tapes for file storage, played on a proprietary player connected using a 5-pin DIN connector.


A cartridge port was available. A RAM expansion adding extra 64 KB could be plugged into it, but was incompatible early MO5 machines.[7]


Around 200 software titles are known to exist for the MO5.[8]


An improved version, named Thomson MO5E ("E" for "Export", a model designed for foreign markets) was presented in 1985. It had a different casing featuring a mechanical keyboard, a parallel port, two joystick ports, an internal PAL modulator and an integrated power supply.[9]

The Thomson MO5NR ("NR" for "Nanoréseau", a network standard) was introduced in 1986 and added a 58 key AZERTY keyboard and an integrated network controller.[10]


  1. ^ a b "MO5 v3 Circuit Diagram".
  2. ^ a b "Thomson MO5 Emulation in MESS".
  3. ^ a b "Thomson MO5". Archived from the original on 4 July 2018.
  4. ^ a b c d "documentations:hardware:mo5 [DON'T PANIC]".
  5. ^ a b c d Oury, Michel (1985). "Manuel Technique du MO5" (PDF).
  6. ^ a b c "documentations:devices:gate.arrays [DON'T PANIC]".
  7. ^ "documentations:expansions:ram [DON'T PANIC]".
  8. ^ "Listing of all Thomson MO5 games - Page 1". The Video Games Museum.
  9. ^ "OLD-COMPUTERS.COM : The Museum".
  10. ^ "Thomson MO5NR MESS driver". Archived from the original on 2021-06-05.

External linksEdit

  • DCMOTO: PC emulator for Thomson MO5, MO5E, MO5NR, MO6, T9000, TO7, TO7/70, TO8, TO8D, TO9, TO9+ and Olivetti Prodest PC128. Comprehensive software and documentation are also available.
  • MO5 at