Acorn Risc PC 600: Difference between revisions
Rewrite from Risc PC TRM and Chris's Acorns: PSU outputs and tolerances (p. E-1), board, battery and capacitor counts, backplane 7905; fix board issues (C and D, not A); cite leakage to stardot; link newly hosted TRM drawings |
Restore 70% width so the table sits beside the infobox |
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== Architecture == | == Architecture == | ||
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|+'''Risc PC 600 main chips (Technical Reference Manual, Part 1)''' | |+'''Risc PC 600 main chips (Technical Reference Manual, Part 1)''' | ||
! Function !! Device !! Notes | ! Function !! Device !! Notes | ||
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The power supply gives +5.1 V, +12 V and −12 V to the main board on a six-way connector (red +5 V, black 0 V, yellow +12 V, blue −12 V). It is selectable for 198–254 V or 98–132 V mains.<ref name="trm" /> The −5 V for expansion cards comes from a 7905 regulator on the backplane.<ref name="trm" /> | The power supply gives +5.1 V, +12 V and −12 V to the main board on a six-way connector (red +5 V, black 0 V, yellow +12 V, blue −12 V). It is selectable for 198–254 V or 98–132 V mains.<ref name="trm" /> The −5 V for expansion cards comes from a 7905 regulator on the backplane.<ref name="trm" /> | ||
{| class="wikitable styled-table" style="width: | {| class="wikitable styled-table" style="width:70%; text-align:center;" | ||
|+'''Risc PC power supply outputs (Technical Reference Manual p. E-1)''' | |+'''Risc PC power supply outputs (Technical Reference Manual p. E-1)''' | ||
! Output !! Tolerance !! 70 W supply, max continuous !! 103 W supply, max continuous !! Ripple and noise | ! Output !! Tolerance !! 70 W supply, max continuous !! 103 W supply, max continuous !! Ripple and noise | ||
Latest revision as of 20:18, 1 October 2026
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| Acorn publicity photograph of the Risc PC 600 (1994) | |
| Specifications | |
|---|---|
| Manufacturer | Acorn Computers Ltd |
| Type | Desktop computer |
| Released | April 1994 |
| Intro price | £1,249–1,699 ex VAT (1994)[1] |
| CPU | ARM610 at 30 MHz on a plug-in card (33 MHz from July 1995) |
| Memory | Two 72-pin DRAM SIMM sockets, up to 256 MB; optional 1 or 2 MB VRAM |
| Storage | 3.5-inch floppy; IDE hard disc; CD-ROM on some models |
| Display | VIDC20; 1- to 32-bit pixel depths |
| Sound | 8-channel, 8-bit (16-bit from July 1995) |
| OS / Firmware | RISC OS 3.50 (3.60 from July 1995) |
| Model no. | ACB15, ACB25, ACB45 and later variants |
The Acorn Risc PC 600 is a desktop computer that Acorn Computers launched in April 1994. It has a 30 MHz ARM610 processor on a plug-in card and a new chip set, IOMD and VIDC20, in place of the MEMC, IOC and VIDC of the Archimedes. It shipped with RISC OS 3.50.[2] The case is built from stackable sections, and extra sections add drive bays and expansion slots.[3]
Architecture
[edit | edit source]| Function | Device | Notes |
|---|---|---|
| Processor | ARM610, 30 MHz | On a plug-in card (0197,208) in one of two processor slots; on-chip MMU and 4 KB cache |
| Memory and I/O controller | IOMD | DRAM control for two SIMMs, VRAM control, sound and I/O DMA, expansion bus |
| Video and sound | VIDC20 | 1, 2, 4, 8, 16 and 32-bit pixels; pixel rates above 110 MHz |
| Peripheral controller | SMC FDC37C665 | Floppy, IDE, serial and parallel |
| Clock and CMOS RAM | PCF8583 | On the I²C bus, backed by BT1 |
The processor card plugs into one of two OPEN Bus slots; the other can take a second processor, and Acorn and others made x86 "PC cards" for it.[3][1] Main memory is in two 72-pin DRAM SIMM sockets, up to 256 MB, and VRAM is on a plug-in card in a DIMM socket.[3] The Risc PC was Acorn's first machine with dedicated video RAM, and VIDC20 was its first video controller able to show more than 256 colours.[1]
Expansion cards plug into a backplane on the 132-way edge connector of the main board. Acorn made 2-slot (0197,101) and 4-slot (0197,001) backplanes, and the architecture allows up to eight slots. A separate network slot takes Econet or Ethernet cards.[3] The keyboard is a standard PC-AT type; the mouse is Acorn's three-button design.[2]
Power supply
[edit | edit source]The power supply gives +5.1 V, +12 V and −12 V to the main board on a six-way connector (red +5 V, black 0 V, yellow +12 V, blue −12 V). It is selectable for 198–254 V or 98–132 V mains.[3] The −5 V for expansion cards comes from a 7905 regulator on the backplane.[3]
| Output | Tolerance | 70 W supply, max continuous | 103 W supply, max continuous | Ripple and noise |
|---|---|---|---|---|
| +5.1 V | +2 %, −4 % (4.90–5.20 V) | 7.90 A | 11.00 A | 50 mV |
| +12 V | ±7 % | 2.05 A | 3.60 A | 100 mV |
| −12 V | ±7 % | 0.25 A | 0.25 A | 50 mV |
The 70 W supply is for machines with no backplane or the 2-slot backplane. The 4-slot backplane needs the 103 W supply.[3]
Main board
[edit | edit source]The main PCB is 0197,000; Acorn's circuit diagram (drawing 0197,000/C) is titled "Medusa main PCB".[3][4] Chris Whytehead's two Risc PC 600 boards are issue C and issue D.[2] The board carries:
- BT1, a 1.2 V 280 mAh nickel-metal hydride cell (Acorn 0817,016) that backs the PCF8583 clock and CMOS RAM. It is charged from +5 V through D2 and R130 (180 Ω) while the machine is on.[3][4]
- Two surface-mount fuses, FS1 (2 A) and FS2 (800 mA).[3]
- 27 surface-mount aluminium electrolytic capacitors, three surface-mount tantalums and eight radial electrolytics.[3]
Owners on stardot have reported electrolyte leaking from the surface-mount capacitors, and leakage from the battery spreading across the board.[5][6] Repair is covered on Acorn Risc PC 600 Maintenance Guide and Acorn Risc PC 600 Capacitor Guide.
Models
[edit | edit source]The launch models were the ACB15 (2 MB, 210 MB hard disc), ACB25 (4 MB, 1 MB VRAM, 210 MB) and ACB45 (8 MB, 1 MB VRAM, 420 MB, second case section). The Risc PC 600 CD models (ACB28 and ACB48) followed in January 1995 with an Acorn 300i CD-ROM drive. In July 1995, when the Acorn Risc PC 700 was launched, the 600 moved to a 33 MHz ARM610, 16-bit sound and RISC OS 3.60 (models ACB60 to ACB69). Acorn also sold software bundles (ACB80 to ACB88) and X Window terminal versions (ACB98 and ACB99).[2]
Documentation
[edit | edit source]- Acorn Risc PC Technical Reference Manual (0497,057, 1994): system description, interfaces, parts lists, POST, power supply data.[3]
- File:Acorn Risc PC Technical Reference Manual drawings.pdf: the manual's 22 engineering drawings, including the main PCB circuit diagram.[4]
Related pages
[edit | edit source]- Acorn Risc PC 600 Maintenance Guide
- Acorn Risc PC 600 Troubleshooting Guide
- Acorn Risc PC 600 Capacitor Guide
- Acorn Risc PC 700
- Acorn Archimedes A5000
References
[edit | edit source]- ↑ 1.0 1.1 1.2 "The Acorn Risc PC and A7000", 4corn Computers (retrieved 2026-10-01). Launch price £1,249–1,699 ex VAT; ARM610 with on-chip MMU; VIDC20 with up to 16 million colours; 16-bit sound not fitted as standard on early machines; first Acorn machine with dedicated VRAM; up to 8 podules; x86 guest processors from a 33 MHz 486 to a 133 MHz IBM 586; RISC OS 3.50.
- ↑ 2.0 2.1 2.2 2.3 Whytehead, Chris. "Acorn Risc PC 600", Chris's Acorns, archived by The Centre for Computing History (retrieved 2026-10-01). April 1994 launch; ARM610 at 30 MHz; RISC OS 3.50; VIDC20 and IOMD; up to 256 MB in DRAM SIMMs and optional 1 or 2 MB VRAM; PC AT keyboard and Acorn three-button mouse; 8-channel 8-bit sound; two podule slots and a separate network slot; model list; July 1995 upgrade to a 33 MHz ARM610, 16-bit sound and RISC OS 3.60; Chris's machines have main boards 0197,000 issue C and issue D and ARM610 card 0197,208.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 Acorn Computers, Risc PC Technical Reference Manual, part no. 0497,057, issue 1, September 1994, hosted on this wiki. System description pp. 1-1 to 1-34 (features p. 1-3, battery p. 1-10, backplanes and power requirements p. 1-21); parts lists pp. 3-1 to 3-11; Power On Self Test p. A-1; power supply and mechanical data pp. E-1 and E-2.
- ↑ 4.0 4.1 4.2 Acorn Computers, Risc PC engineering drawings (Technical Reference Manual Appendix C), 1994: main PCB circuit diagram 0197,000/C sheets 1–7, main PCB assembly, ARM610 card, VRAM cards, backplanes and final assembly. Hosted on this wiki as File:Acorn Risc PC Technical Reference Manual drawings.pdf.
- ↑ "RISC PC motherboard refurbish", stardot.org.uk forum thread, July 2020 to March 2022. sP1d3r found electrolyte leaking from the surface-mount electrolytics and none passing an in-circuit ESR test; danielj reported C122 leaking on an issue 1 board, giving an unstable picture in high-resolution modes.
- ↑ "Where to start resurrecting a RiscPC 700", stardot.org.uk forum thread, April–May 2018. A corroded battery whose leakage had spread down the board to the reset switch; cleaning with white vinegar, rinsing and drying before power-up.