Acorn A7000
 | |
| A7000 (AMC23) with an Acorn monitor | |
| Specifications | |
|---|---|
| Manufacturer | Acorn Computers |
| Type | Desktop computer |
| Released | July 1995[1] |
| CPU | ARM7500 at 32 MHz |
| Memory | 2, 4 or 8 MB on the board, plus one SIMM socket |
| Storage | 3.5-inch floppy drive; IDE hard disc; optional ATAPI CD-ROM |
| Display | Up to 1280 × 1024; up to 24 bits per pixel at lower resolutions |
| Sound | 16-bit stereo |
| ROM | 4 MB (RISC OS 3.60) |
| Power | Internal 35 W switch-mode supply |
| Dimensions | 357 × 283 × 102 mm |
| Weight | About 4 kg |
| OS / Firmware | RISC OS 3.60 |
| Predecessor | Acorn Archimedes A5000 |
| Successor | Acorn A7000+ |
| Model no. | AMC01 to AMC05, AMC21 to AMC25, CON10 |
The Acorn A7000 is a RISC OS desktop computer launched by Acorn in July 1995 as a lower-cost relative of the Risc PC.[1] It is built around the ARM7500, a single chip that combines an ARM7 processor core with a video controller similar to the Risc PC's VIDC20 and most of the functions of its IOMD I/O controller. Acorn described the chip as "almost a Risc PC on a chip".[2] It was followed in 1997 by the faster Acorn A7000+, which shares its case and most of its design.[3]
Differences from the Risc PC
[edit | edit source]Chris Whytehead lists what Acorn left out to make the A7000 cheaper to build:[1]
- The ARM7500 is surface-mounted, so the processor cannot be upgraded.
- There is no second processor slot, so no PC cards.
- There is no VRAM; the screen memory comes from main memory.
- There is no backplane. An optional one-slot backplane takes a single expansion card, and it cannot be fitted together with a CD-ROM drive.
- There is one DRAM slot (the Risc PC has two).
- The keyboard and mouse are PS/2 types, so standard PC keyboards and mice can be used.
Specification
[edit | edit source]| Item | Specification |
|---|---|
| Processor | ARM7500, 32 MHz, 4 KB cache |
| Memory | 2, 4 or 8 MB fast page mode DRAM on the board plus one SIMM socket (maximum 136 MB); 4 MB ROM; 240 bytes of battery-backed CMOS RAM |
| Storage | 3.5-inch floppy drive (2 MB unformatted); IDE hard disc (425 MB standard); ATAPI CD-ROM option in the 5.25-inch bay |
| Video | 15-way VGA connector; modes include 1280 × 1024 at 2 bpp, 1024 × 768 at 4 bpp, 800 × 600 and 640 × 480 at 8 bpp, 480 × 352 at 16 bpp, 240 × 352 at 24 bpp; internal genlock port |
| Sound | 16-bit stereo with a mixer for a CD-ROM, 3.5 mm jack for 32 ohm headphones or line out, internal speaker |
| Ports | 9-pin serial, 25-pin parallel, PS/2 keyboard, PS/2 three-button mouse |
| Expansion | Network slot (Ethernet or ATM); one expansion card slot |
| Power | Integral 35 W switch-mode supply, IEC inlet and outlet, auto-ranging 110 to 240 V AC |
| Size and weight | 357 × 283 × 102 mm; about 4 kg |
Source: Acorn Risc Technologies.[4] Chris Whytehead's A7000 runs its memory at 16 MHz.[1] On performance, the datasheet says "around 29 MIPS (Dhrystone 2.1) peak", Acorn's ARM7500 leaflet gives the A7000 25 MIPS, and Chris Whytehead measured 17.87 MIPS (ARMSi) and 24,252 Dhrystones per second on his machine.[4][2][1]
Models
[edit | edit source]| Code | Configuration |
|---|---|
| AMC01 | 2 MB, network interface |
| AMC02 | 2 MB, 425 MB hard disc |
| AMC03 | 4 MB, 425 MB hard disc |
| AMC04 | 4 MB, network interface |
| AMC05 | 4 MB, 540 MB hard disc |
| AMC21 | 2 MB, network interface, CD-ROM |
| AMC22 | 2 MB, 425 MB hard disc, CD-ROM |
| AMC23 | 4 MB, 425 MB hard disc, CD-ROM |
| AMC25 | 4 MB, 540 MB hard disc, quad-speed CD-ROM |
| CON10 | 2 MB, 425 MB hard disc (Early Years) |
Hardware
[edit | edit source]
Chris Whytehead's A7000 has main board 1102,005 with a VLSI VY27073B ARM7500. The board carries the SIMM socket, the two RISC OS ROMs, the backplane slot, the IDE and floppy connectors with the CMOS backup battery above them, the network card socket and the power supply connectors.[1] The floppy, IDE, serial and parallel interfaces come from an SMC "Super I/O" controller beside the battery. Stardot members identify it as the FDC37C665, the part used on the Risc PC; Theo Markettos's notes suggest the FDC37C669 for the A7000.[5][6]
The power supply provides +5 V, +12 V and −12 V.[7] Acorn's datasheet describes it as auto-ranging from 110 to 240 V; one owner's A7000+ supply is labelled for 220 to 240 V only, so read the label before using one on 110 V mains.[4][8]
Acorn never published a circuit diagram of the A7000 board, as far as stardot members know, so repairers trace faults with the Risc PC drawings.[6]
Maintenance and repair
[edit | edit source]The main age problem is the CMOS backup battery, which leaks onto the tracks around the floppy and IDE controller.[6][9] See Acorn A7000 Maintenance Guide and Acorn A7000 Troubleshooting Guide.
Documentation
[edit | edit source]- Acorn A7000 Documentation: the ART datasheet, the ARM7500 leaflet and the A7000+ leaflet.
- Acorn Risc PC Technical Reference Manual and its drawings, for the parts of the design the A7000 shares.
Related pages
[edit | edit source]- Acorn A7000+
- Acorn A7000 Maintenance Guide
- Acorn A7000 Troubleshooting Guide
- Acorn Risc PC 600
- Acorn Archimedes A5000
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Whytehead, Chris. "Acorn A7000", Chris's Acorns, The Centre for Computing History (retrieved 2026-10-01). Launched July 1995; differences from the Risc PC; model list; his AMC23: main board 1102,005, VLSI VY27073B ARM7500 at 32 MHz, IOMD functions, 4 MB on board plus 16 MB EDO SIMM, memory clock 16 MHz, TEAC FD-235HF floppy, Seagate ST3660A hard disc, Sony CDU77E-Q6 CD-ROM, RISC OS 3.60 dated 13 April 1995, 24,252 Dhrystones and 17.87 MIPS; CMOS battery above the IDE and floppy connectors; network slot, backplane slot and power connectors on the board.
- ↑ 2.0 2.1 Acorn Computers, leaflet "ARM7500", APP 868, first edition July 1995. Hosted on this wiki: File:Acorn ARM7500 leaflet (APP868).pdf. ARM704 core, VIDC20-like video, most of IOMD, two PS/2 ports, joystick interface; benchmark table giving the A7000 25 MIPS.
- ↑ Whytehead, Chris. "Acorn A7000+", Chris's Acorns (retrieved 2026-10-01). Launched May 1997; 48 MHz ARM7500FE, 8 MB EDO, 1.2 GB disc, RISC OS 3.71; the only visible difference is the '+'; Castle continued production.
- ↑ 4.0 4.1 4.2 Acorn Risc Technologies, datasheet "A7000", DS002/ART/RK, February 1996. Hosted on this wiki: File:Acorn A7000 datasheet (ART DS002).pdf.
- ↑ Markettos, Theo. "Acorn/RISC OS technical documents and hardware resources" (retrieved 2026-10-01): FDC37C665GT "IO chip used in the Risc PC"; FDC37C669 "IO chip used in the NC, Bush STB, and I think A7000(+)".
- ↑ 6.0 6.1 6.2 "A7000 floppy / HD issues", stardot.org.uk forum thread, February 2017 to December 2024. danielj and sirbod on the FDC37C665 next to the battery and its sensitivity to static and battery damage; sirbod's track repairs under the C13 legend; stevepick on the IDE connector fitted backwards; IanJeffray on the unpublished schematics.
- ↑ "A7000+ with new caps, but it's dead Jim", stardot.org.uk forum thread, July to August 2022. cosworthchris: flickering power LED and clicking speaker cured by replacing a dried-out small capacitor in the supply, giving 12 V, −12 V and 5 V; IanJeffray: no need to recap the main board routinely, test the CMOS circuit and I²C lines, CMOS RAM chips "very regularly die"; sirbod: RISC OS can take about 10 minutes to start if the CMOS chip does not respond.
- ↑ "A7000+ PSU", stardot.org.uk forum thread, August 2018. klintworth's Castle A7000+ supply is marked 220 to 240 V against the brochure's auto-ranging figure.
- ↑ "A7000+ revival, pointers on where to start", stardot.org.uk forum thread, 2017 to 2019. Battery acid damage; vinegar then isopropyl alcohol; jumper wires over the three corroded tracks restored the floppy and IDE; disc error 08 and the Risc PC schematic used for tracing; danielj suggests a NiMH AA in a holder away from the board.