Editing Acorn System 1

{{Infobox computer
| name         = Acorn System 1
| image        = [[File:Acorn System 1.jpg|250px]]
| caption      = Acorn System 1 (Acorn Microcomputer), 1979
| developer    = Sophie Wilson
| manufacturer = Acorn Computers Ltd
| type         = Single-board microcomputer (kit or assembled)
| release date = April 1979
| cpu          = Rockwell R6502 @ 1 MHz
| memory       = 1 KB RAM (2× 2114), 512 bytes ROM (2× 74S571)
| display      = 8-digit 7-segment LED
| sound        = &mdash;
| storage      = CUTS cassette interface (300 baud)
| os           = Monitor in ROM
| predecessor  = &mdash;
| successor    = [[Acorn System 2]], [[Acorn Atom]]
| model        = 200,000 (CPU card), 200,001 (keyboard card)
}}

The '''Acorn System 1''', first sold as the '''Acorn Microcomputer''', was Acorn Computers' first product. It was designed by Sophie Wilson and shipped in April 1979.<ref name="chris1">Whytehead, Chris. [https://chrisacorns.computinghistory.org.uk/Computers/Acorn_Microcomputer.html "Acorn Microcomputer (a.k.a. System 1)"], Chris's Acorns / The Centre for Computing History. Source for the 1978 design by Sophie Wilson, the April 1979 release, the two-Eurocard construction, the CPU-card complement (R6502P, 8154 RAM/IO, 2114 RAM, 74S571 ROM, LM340-T5 regulator), the keyboard-card complement (LED display, hex keypad, CUTS cassette interface) and the board part numbers (200,000 / 200,001).</ref> It was a small machine built on two 100&times;160&nbsp;mm Eurocards, sold as a kit or ready-built, and aimed at hobbyists. The modular, Eurocard-based design led directly to the rack-mounted [[Acorn System 2]] to [[Acorn System 5|System 5]], and the experience fed into the [[Acorn Atom]] and the [[BBC Micro Model A/B|BBC Micro]].<ref name="wp">[https://en.wikipedia.org/wiki/Acorn_System "Acorn System"], Wikipedia. Source for the series overview, the Eurocard modular concept, the per-machine configurations and prices, and the role of the System 3 in Atom and BBC Micro development.</ref>

== The two cards ==

The System 1 is two Eurocards linked by a ribbon cable:<ref name="chris1" /><ref name="s1tech">[[Acorn System 1 Technical Manual]] (Acorn Microcomputer), Acorn Computers &mdash; hosted on this wiki. Source for the CPU-card and keyboard-card IC and capacitor parts lists, the construction notes and the circuit description.</ref>

{| class="wikitable styled-table" style="width:70%; text-align:center;"
|+'''Acorn System 1 cards'''
! Card !! Part !! Key devices
|-
| CPU card || 200,000 || Rockwell R6502 @ 1 MHz; 2× INS8154 RAM/IO; 2× 2114 (1 KB RAM); 2× 74S571 (512 bytes ROM); LM340-T5 5 V regulator; 1 MHz crystal
|-
| Keyboard / cassette card || 200,001 || 8-digit 7-segment LED display; 25-key hex keypad; CUTS 300-baud cassette interface (LM358 amp, 7445 decoder)
|}

One INS8154 drives the keypad ribbon; the second drives the EuroConnector, so the CPU card can be used unchanged in a [[Acorn System 2|System 2]], 3 or 4. The CPU card also has an empty socket for a 2516 EPROM and a second 8154.<ref name="chris1" />

== Operation ==

The monitor program in the 512-byte ROM lets the user examine and modify memory and registers through the hex keypad and the 8-digit LED display, and save or load via the CUTS cassette interface at 300 baud. There is no video output on the base machine; a VDU requires a [[Acorn System 2|System 2]]-style frame with a VDU Eurocard.

== Maintenance and repair ==

* [[Acorn System 1 Maintenance Guide]]
* [[Acorn System 1 Troubleshooting Guide]]
* [[Acorn System 1 Capacitor Replacement Guide]]

== Documentation ==

* [[Acorn System 1 User Manual]]
* [[Acorn System 1 Technical Manual]]
* [[Acorn System 1 Circuit Diagrams]]

== See also ==

* [[Acorn System 2]] · [[Acorn System 3]] · [[Acorn System 4]] · [[Acorn System 5]]
* [[Acorn Atom]] &mdash; the all-in-one home computer derived from this work

== References ==

<references />

{{Navbox-AcornComputers}}

[[Category:Acorn Computers]]