Acorn System 4
 | |
| Acorn System 4 rack with some Eurocards fitted (photo: Chris's Acorns) | |
| Specifications | |
|---|---|
| Manufacturer | Acorn Computers Ltd |
| Type | Eurocard microcomputer with twin floppy discs, assembled only |
| Intro price | £1,525 with case, power supply and 16 KB RAM (1982) |
| CPU | 6502 at 1 MHz |
| Memory | 16 KB RAM (basic system) |
| Storage | Two 5.25-inch floppy disc drives |
| Display | VDU interface card |
| Sound | — |
| OS / Firmware | Acorn Disk Operating System |
| Predecessor | Acorn System 3 |
| Successor | Acorn System 5 |
The Acorn System 4 is the largest of Acorn's early Eurocard systems: a double-height rack with room for 14 Eurocards in the lower frame and two floppy disc drives above them. Acorn's sales sheet lists the basic system as two floppy drives, power supplies, card frame, buffered backplane, 6502 CPU, VDU interface, 16 KB of RAM and a disc controller, with a disc operating system and a utilities disc. Unlike the System 1 to 3, it was not sold as a kit.[1] In 1982 it cost £1,525 with case, power supply and 16 KB of RAM, plus extra for the keyboard.[2]
Cards
The basic System 4 uses the same card types as the Acorn System 3: the 6502 CPU card, a VDU interface card, RAM and the floppy disc controller.[1][3] The machine in Acorn's sales sheet also has a cassette interface, 32 KB of RAM, a Versatile Interface Board for serial and parallel ports, an analogue to digital converter, a PROM programmer and an in-circuit emulator.[1]
Chris Whytehead's System 4 case, donated by Ben Harris, holds a 6502 CPU card with a connector for the Acorn System keyboard, an 8 KB static RAM card, a 40-column VDU card, an Econet card, a Universal Interface Board and a bus extender, on a 14-slot backplane.[3]
| Card | Board | Document |
|---|---|---|
| 6502 CPU | 200,000 | Acorn System 1 Circuit Diagrams; Acorn System 1 Technical Manual |
| Teletext VDU | 200,002 | File:Acorn teletext VDU interface Eurocard circuit diagram (200,002).png |
| 8K RAM and 8K PROM | 200,003 | File:Acorn 8K RAM and 8K PROM Eurocard circuit diagram (200,003).png |
| Floppy disc controller | 200,004 | File:Acorn floppy disc controller Eurocard circuit diagram (200,004).png |
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Maintenance and repair
- Acorn System 4 Maintenance Guide
- Acorn System 4 Troubleshooting Guide
- Acorn System 4 Capacitor Replacement Guide
Documentation
- Acorn System 4 Brochure: Acorn's sales sheet.
- File:Acorn System 2 Technical Manual (text transcription).pdf: the CPU, VDU and memory cards as used in the System 2.
- Acorn System Catalogue: the Eurocard range.
Related pages
References
- ↑ 1.0 1.1 1.2 Acorn Computers, Acorn System 4 Computer, one-page sales sheet, undated. Hosted on this wiki as File:Acorn System 4 brochure.pdf.
- ↑ "Acorn System", Wikipedia (retrieved 2026-10-01). System 4: double-height frame with fourteen slots below and two floppy drives above; 1982 price £1,525 with casing, power supply and 16K of RAM.
- ↑ 3.0 3.1 Whytehead, Chris. "Acorn System 4", Chris's Acorns, archived by The Centre for Computing History (retrieved 2026-10-01). Double-height rack for up to 14 Eurocards; minimum configuration; Chris's System 4 case (donated by Ben Harris) holds a 1 MHz 6502 CPU with a System keyboard connector, an 8K static RAM card, a 40-column VDU card, an Econet card, a Universal Interface Board and a Bus Extender, on a 14-slot backplane, with no OS ROM.