The Thomson MO5 is a home computer introduced in France in June 1984 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.
|Media||Cassette tape, Cartridges|
|Operating system||MO5 BASIC 1.0|
|CPU||Motorola 6809E @ 1 MHz|
|Memory||32 KB RAM, 16 KB VRAM|
|Display||320x240, 8 colours with 2 saturation variations, 2 colours per 8x1 pixel area|
|Graphics||EFGJ03L gate array|
|Sound||1-bit square wave|
|Related articles||Thomson 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. The computer boots directly to the built-in Microsoft BASIC interpreter (MO5 Basic 1.0).
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).
Graphics were generated by a EFGJ03L (or MA4Q-1200) gate array capable of 40×25 text display and a resolution of 320 x 200 pixels with 16 colours (limited by 8x1 pixel colour attribute areas).. 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"). 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.  This approach allows the display of Orange instead of "desaturated white", and Gray instead of "desaturated black".
|Thomson MO5 Hardware Palette|
|PROM bit mask
B2B1 G2G1 R2R1
|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. The video output is RGB on a SCART connector, with the refresh rate being 625-line compatible 50Hz.
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.
Around 200 software titles are known to exist for the MO5.
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.