Acorn System 3
 | |
| Acorn System 3 (photo: Chris's Acorns) | |
| Specifications | |
|---|---|
| Manufacturer | Acorn Computers Ltd |
| Type | Eurocard microcomputer with floppy disc |
| Intro price | £775, or £1,075 with power supply, case and two more 8 KB RAM cards; keyboard £136 (1982) |
| CPU | 6502 at 1 MHz (6809 card available) |
| Memory | 8 KB RAM with 4 KB BASIC ROM (minimum) |
| Storage | 5.25-inch floppy disc, 100 KB; Intel 8271 controller |
| Display | 40 × 25 teletext VDU card (80 × 25 card available) |
| Sound | — |
| OS / Firmware | Acorn DOS; FLEX with the 6809 card |
| Predecessor | Acorn System 2 |
| Successor | Acorn System 4 |
The Acorn System 3 is the disc-based member of Acorn's Eurocard range. It replaces the cassette interface card and Cassette Operating System of the Acorn System 2 with a floppy disc controller card, a 5.25-inch drive in the card frame and a disc operating system ROM.[1] Wikipedia describes it as the standard development machine in Acorn's lab: the Acorn Atom has been called a cut-down System 3, and much of the BBC Micro's development was done on one.[1] Chris Whytehead also describes the Atom as a System 3 in a new case.[2]
Configuration
[edit | edit source]The minimum System 3 has:[1][3]
| Card | Board | Notes |
|---|---|---|
| 6502 CPU, 1 MHz | 200,000 | The System 1 and 2 processor card[4] |
| VDU interface | 200,002 | 40 × 25 teletext (MC6845, SAA5050)[5] |
| Memory | 200,003 | 8 KB of 2114 RAM and the 4 KB BASIC ROM[6] |
| Floppy disc controller | 200,004 | Intel 8271 controller, 4 MHz clock[7] |
| Disc drive | – | One 100 KB 5.25-inch drive in the card frame |
Acorn also made a 6809 processor card, which turned the System 3 into a disc system running the FLEX operating system, and an 80 × 25 VDU card.[3] The cassette interface card from the System 2 can be added.[4] In 1982 the System 3 cost £775, or £1,075 with power supply, case and two more 8 KB RAM cards, plus £136 for the keyboard.[1]
Maintenance and repair
[edit | edit source]- Acorn System 3 Maintenance Guide
- Acorn System 3 Troubleshooting Guide
- Acorn System 3 Capacitor Replacement Guide
Documentation
[edit | edit source]- File:Acorn floppy disc controller Eurocard circuit diagram (200,004).png, File:Acorn teletext VDU interface Eurocard circuit diagram (200,002).png and File:Acorn 8K RAM and 8K PROM Eurocard circuit diagram (200,003).png: Acorn's drawings of the System 3 cards.
- Acorn System 2 Technical Manual (PDF): the CPU, VDU and memory cards as set up for the System 2.
- Acorn System 1 Technical Manual and Acorn System 1 Circuit Diagrams: the CPU card.
- Acorn System Catalogue: the Eurocard range.
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Related pages
[edit | edit source]References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 "Acorn System", Wikipedia (retrieved 2026-10-01). System 3: floppy disc controller, drive and DOS ROM in place of the System 2's cassette card and COS; minimum configuration; 1982 prices; the Atom called a cut-down System 3; BBC Micro development done on the System 3.
- ↑ Whytehead, Chris. "Acorn Atom", Chris's Acorns, archived by The Centre for Computing History (retrieved 2026-10-01). "The Atom is based on a System 3 in a new case with keyboard."
- ↑ 3.0 3.1 Whytehead, Chris. "Acorn System 3", Chris's Acorns, archived by The Centre for Computing History (retrieved 2026-10-01). Minimum configuration; 6809 CPU card for FLEX; Chris's machine has an 80 × 25 VDU card, three memory cards, a 6809 CPU card, a custom RS232 card, the floppy disc controller card and two Tandon 40-track single-sided drives, one in the card frame.
- ↑ 4.0 4.1 Acorn Computers, Acorn System Catalogue (undated sales catalogue), hosted on this wiki. 6502 CPU card designed for the Systems 2, 3 and 4 (p. 11); cassette interface card can be added to the Systems 3, 4 and 5 (p. 18).
- ↑ Acorn Computers, V.D.U. Interface PCB (Teletext), circuit diagram 200,002/C, 1979. Hosted on this wiki as File:Acorn teletext VDU interface Eurocard circuit diagram (200,002).png.
- ↑ Acorn Computers, 8K RAM + 8K PROM Eurocard circuit diagram 200,003/C, issue 1, 1979. Hosted on this wiki as File:Acorn 8K RAM and 8K PROM Eurocard circuit diagram (200,003).png.
- ↑ Acorn Computers, Floppy Disc Controller PCB Circuit Diagram, 200,004/C, issue 1, 7 February 1980. Hosted on this wiki as File:Acorn floppy disc controller Eurocard circuit diagram (200,004).png.