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Acorn 6809 CPU

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Acorn 6809 CPU

From the early days of Acorn, 1979-80, this is a 6809 CPU card which could be used as an alternative to the 6502 CPU card in the System 3 computer. It ran the Flex operating system. The socket on the right hand end is for the parallel System keyboard.

Here is the brochure for the Acorn 6809 card.

I have a System 3 with a 6809 CPU card:

Acorn 6809 CPU front

Acorn 6809 CPU (front)

This 6809 CPU has a front panel fitted with a reset switch about the parallel keyboard connector at the top and a printer interface fitted at the bottom. The part no. is 200,012 issue 2. Here is a hi-res picture.

Acorn 6809 CPU back

Acorn 6809 CPU (back)

This Eurocard is a plug in replacement for the 6502 CPU card to upgrade Acorn Systems 3 and 4 to use the advanced facilities of Motorola's 6809 8-bit processor and is ideally suited to run high level languages such as Pascal. The Acorn 6809 is provided with an operating system in 2K which handles the Acorn VDU, ACSII encoded keyboard and printer; it is readily expanded and very user friendly.

The hardware provides for direct plug-in connection to Centronics type printers and encoded keyboards and all 6809 signals are taken off the board via the Acorn bus 64-way edge connector. The address and data lines are buffered and 1K of user RAM is provided. The major components fitted are:-

DIN standard indirect edge connector,
20-way and 36-way IDC edge connectors for keyboard and printer.
MC 6809 microprocessor.
2K ROM(Initially 2716) 4K and 8K compatible.
1K RAM (2 x 2114).
BIPOLAR PROM for address decoding.
6522 two ten bit parallel i/o ports for keyboard and printer.
Random logic devices for address decoding.
Bus buffers.

The Acorn 6809 is provided with a User's Manual which described how to use the monitor commands, and includes programming examples. Here is the Acorn 6809 User's manual .

An international standard disk operating system, called FLEX, is available to run with this card. This system allows the user access to disk files on a System 3 or System 4, and to buy standard software from software houses to run under FLEX.