Acorn R225
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| Acorn's drawing of the system unit shared by the A540, R260 and R225. The R225 has no floppy drive or hard disc light. | |
| Specifications | |
|---|---|
| Manufacturer | Acorn Computers |
| Type | Discless Unix workstation |
| Released | June 1990 |
| Intro price | £1,995 ex VAT |
| CPU | ARM3 on a plug-in processor card |
| Memory | 4 MB |
| Storage | None; boots over Ethernet |
| Display | — |
| Sound | — |
| OS / Firmware | RISC iX (4.3BSD Unix), from a file server or an R260 |
| Model no. | UNX22 |
The Acorn R225 is the discless member of Acorn's R200 series of Unix workstations, released in June 1990 alongside the Acorn R260. It has the R260's ARM3 hardware with 4 MB of RAM and an Ethernet card, but no floppy drive and no hard disc. RISC iX was installed on a file server, or an R225 could boot from a networked R260.[1][2] Wikipedia gives its price as £1,995 ex VAT, down from an announced £3,000.[2]
The R225 shares its main board, case, power supply and service manual with the R260 and the Acorn Archimedes A540. The board, power supply, capacitors and backup battery are described on the A540 page, and the self-test, fault codes and RISC iX notes on the Acorn R260 page.[3] Chris Whytehead has not seen an R225, and no photograph of one has been found; the infobox shows Acorn's drawing of the shared case.[1]
Differences from the R260
[edit | edit source]Acorn's service manual and installation guide list what is different about the R225:[3][4]
| Item | R225 | R260 |
|---|---|---|
| Floppy drive | None; the drive bracket is still fitted to stiffen the structure | 3.5-inch drive |
| Hard disc | None, and no hard disc light | SCSI hard disc |
| SCSI card | Not fitted | Fitted |
| Expansion cards fitted | A ROM podule and an Ethernet podule | SCSI and Ethernet cards |
| RAM cards | None (4 MB on the main board) | One 4 MB card (8 MB) |
| Ethernet | Factory-set to the thick Ethernet socket | Thick or thin |
On the desktop an R225 shows no disc icons.[4] When dismantling one, ignore the service manual's references to cables for the floppy and hard disc drives; the disassembly is otherwise the same as for the A540 and R260.[3]
Network and booting
[edit | edit source]The R225 depends on the network for its operating system. Chris Whytehead records that RISC iX had to be installed on a file server by Granada Microcare, or a single R225 could boot from a networked R260.[1] To change the Ethernet card from the thick socket to the thin (Cheapernet) socket, follow the guide supplied with the Ethernet card.[4] On Acorn's Ethernet I card, links LK3 to LK8 make the choice: west (pins a to b) for thick Ethernet, east (pins b to c) for Cheapernet.[5]
Without its server or R260, an R225 has nothing to boot RISC iX from and starts only in RISC OS, which is in ROM. Acorn's installation guide covers fitting expansion cards such as the SCSI card that the R260 and A540 have as standard.[4]
Maintenance and fault finding
[edit | edit source]- The 1.2 V NiCd backup cell BT1 on the main board leaks with age. Remove and inspect it before powering a stored machine; see the A540 page.
- Clean the power supply's air filter at least once a year; the replacement is Acorn part 0816,017.[4]
- The self-test flashes its fault code on the floppy drive light, which the R225 does not have. Use the screen colours, or Acorn's test link or display adaptor, described on the R260 page.[6]
Documentation
[edit | edit source]- Acorn Archimedes 500 Series and R200 Series Service Manual
- Acorn R200 Series Documentation: the installation guide and the circuit and assembly drawings.
Related pages
[edit | edit source]References
[edit | edit source]- ↑ 1.0 1.1 1.2 Whytehead, Chris. "RISC iX Computers", Chris's Acorns, The Centre for Computing History (retrieved 2026-10-02). R225: discless workstation, a variant of the R260, released in June 1990; RISC iX installed on a file server by Granada Microcare, or booted from a networked R260; product UNX22; 4 MB and no hard disc; he has not seen one.
- ↑ 2.0 2.1 "RISC iX", Wikipedia (retrieved 2026-10-02). Section "Hardware": R225 a diskless R260 needing a network file server or an R260 to boot, released alongside the R260 at £1,995 plus VAT after an announced £3,000; RISC iX 1.2 accessible on the R225 via a file server.
- ↑ 3.0 3.1 3.2 Acorn Computers, Acorn Archimedes 500 series / Acorn R200 series Service Manual, part no. 0486,056, issue 2, June 1991. Hosted on this wiki: Acorn Archimedes 500 Series and R200 Series Service Manual. Models covered (About this manual); disassembly notes on the R225 (pp. 3-1 to 3-3).
- ↑ 4.0 4.1 4.2 4.3 4.4 Acorn Computers, Installation Guide for the A540, R260 and R225, part no. 0486,251, issue 1, July 1990. Hosted on this wiki: Acorn R200 Series Documentation. Desktop icons (Switching on); front of the computer (p. 63); Ethernet socket configuration (Appendix A); expansion cards (Appendix D).
- ↑ Acorn Archimedes 500 series / Acorn R200 series Service Manual, part 2, Ethernet I expansion card, links (pp. 2-1 to 2-12).
- ↑ Acorn Archimedes 500 series / Acorn R200 series Service Manual, part 5, power-on self-test (pp. 5-1 to 5-3): fault codes flashed on the floppy drive light "(if fitted)"; test link and display adaptor.