Acorn Microcomputer (a.k.a. System 1)

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Acorn's first ever computer released in 1979 was the System 1. I bought this one on ebay together with the User's and Technical Manuals in June 2003. I have never tried using the System 1, so I don't know if it is working.
An excellent source of further information about the System 1 is Mike Cowlishaw's The Acorn Microprocessor site which includes his PC System 1 emulator.

Manuals and Documents

Here is the System 1 User 's Manual  and ERRATA .

Here is the System 1 Technical Manual and Circuit Diagrams .

System 1

The System 1 consists of 2 Eurocards (100 x 160mm), the first is the 1MHz 6502 CPU card  and the second is the System 1 keyboard card , which are linked together by a ribbon cable.

The CPU card has a 1MHZ crystal and a Rockwell R6502P CPU. It has 2 x NatSemi INS8154 RAM I/O chips, with receivers and drivers for the keypad ribbon cable and the other for the EuroConnector (this allows the CPU card to be used in a System 2, 3 or 4). There are 2 x 2114 providing 1KB of RAM and 2 x 74S571 ROM chips giving 512 Bytes of ROM. There is an empty socket for an 2516 UVPROM (don't know what that would be used for) and the power connector with a 5V regulator.

The keyboard card has a 9 digit 7 segment LCD display, of which 8 digits are used, and a 25 key hexadecimal keypad. The rest of the card is the CUTS (Computer Users Tape Standard) 300 baud cassette interface.

 Acorn System 1

System 1 showing keyboard and LEDs

 Acorn System 1 showing CPU card

System 1 partially disassembled to show the processor board

 Acorn Microcomputer Manuals

System 1 Manuals.


Serial No.n/a
Motherboard part no
Keyboard part no..
CPURockwell R6502P
CPU Clock1MHz
ROM512 Bytes