Acorn A4
 | |
| Acorn A4 with the lid open | |
| Specifications | |
|---|---|
| Manufacturer | Acorn Computers |
| Type | Portable computer |
| Released | June 1992[1] |
| Intro price | £1,399 ex VAT (2 MB); £1,699 ex VAT (4 MB, 60 MB hard disc)[2] |
| CPU | ARM3 at 24 MHz (6 MHz in power-save mode) |
| Memory | 2 MB or 4 MB |
| Storage | 3.5-inch floppy drive; 2.5-inch 60 MB IDE hard disc on the 4 MB model |
| Display | 640 × 480 monochrome LCD, 15 grey shades, edge-lit; VGA output |
| Sound | — |
| ROM | 2 MB (RISC OS 3), plus an extension ROM for power management |
| Power | 14.4 V 1800 mAh NiCd battery pack; external mains adaptor |
| Dimensions | 297 × 210 × 53 mm |
| Weight | 2.3 kg without battery |
| OS / Firmware | RISC OS 3 |
| Model no. | AKB62, AKB64, AKB66 |
The Acorn A4 is Acorn Computers' only portable computer, launched in June 1992. It is an ARM3 RISC OS machine of the same generation as the Acorn Archimedes A5000, built into a case the size of a sheet of A4 paper, with a monochrome LCD, an internal floppy drive, an optional 2.5-inch IDE hard disc and a nickel-cadmium battery pack.[1][2] Acorn's design name for it was Perth: the main board, display unit and keyboard are all "Perth" assemblies in the parts lists.[3]
Acorn launched two versions: a 2 MB machine with the floppy drive only at £1,399 ex VAT (£1,099 to education) and a 4 MB machine with a 60 MB hard disc at £1,699 (£1,399 to education), with volume shipments planned from September 1992.[2] Chris Whytehead records the models AKB62 (2 MB), AKB64 (4 MB, 60 MB hard disc) and AKB66 (4 MB, 80 MB hard disc).[1] The case parts are marked "TA/Acorn"; Chris Whytehead says Acorn used a Triumph-Adler case, and Theo Markettos identifies the Triumph-Adler Walkstation as the PC laptop the A4 was based on.[3][1][4]
Specification
| Item | Specification |
|---|---|
| Processor | ARM3 with 4 KB cache, 24 MHz (6 MHz in automatic power-save mode) |
| Memory | 2 MB (model I) or 4 MB (model II); memory clock 12 MHz (3 MHz in power-save) |
| ROM | 2 MB operating system ROM |
| Floppy drive | 3.5-inch, 2 MB unformatted; ADFS 1.6 MB, 800 KB and 640 KB; DOS 1.44 MB and 720 KB |
| Hard disc | 2.5-inch 60 MB IDE (model II), auto-parking, configurable spin-down |
| Display | Twin-layer formulated twisted nematic LCD, 640 × 480, 15 grey shades, fluorescent edge light with brightness control |
| Video out | 15-pin VGA; VGA, 256-colour VGA and 800 × 600 SuperVGA; automatic monitor detection |
| Ports | 25-pin parallel (bi-directional); 9-pin RS232 (AT pinout); 6-pin mini-DIN PS/2 keyboard; mouse; stereo headphones |
| Keyboard | Internal 83-key UK PC layout with embedded numeric keypad |
| Battery | 1800 mAh nickel-cadmium pack; 2.5 to 4 hours depending on use |
| Charger | Separate mains adaptor, 100 to 240 V auto-ranging, IEC inlet; quick and trickle charge under control of the power management system, about seven hours to full charge |
| Size and weight | Computer 297 × 210 × 53 mm, 2.3 kg without battery; battery 140 × 111 × 25 mm, 720 g; adaptor 147 × 74 × 44 mm, 420 g |
Source: Acorn's technical specification.[5] The A4 has no built-in pointing device: a three-button mouse plugs into the right-hand side, and the cursor keys with FN can move the pointer.[5][1][6]
Hardware
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The A4 uses the Archimedes chip set: ARM3, MEMC1a, VIDC1a and IOC. An Acorn ASIC called IOEB provides support logic and the clocks for the video modes, a second ASIC (LC) converts the VIDC's output into 16 grey levels for the LCD, and a Chips and Technologies 82C711 handles the floppy drive, serial and parallel ports and the IDE hard disc. A separate Hitachi HD404304F microcontroller, the battery management unit (BMU), runs the charging and the battery gauge.[3] Personal Computer World's review in September 1992 described the board as 10 layers and two-fifths the size of an A4 sheet, and noted that the only significant part of the A5000 left out was the floating point accelerator socket.[7]
| IC | Part | IC | Part |
|---|---|---|---|
| IC23 | ARM3 CPU | IC44 | MEMC1A, 12 MHz |
| IC41 | VIDC1A | IC13 | IOC |
| IC7 | IOEB ASIC | IC12 | LC ASIC (LCD controller) |
| IC34 | 82C711 peripheral controller | IC33 | Battery management controller (HD404304F) |
| IC4, IC15 | RISC OS ROMs 1 and 2 | IC38 | Extension ROM ("RISC OS Green {PORT}") |
| IC6 | 8583 RTC and CMOS RAM | IC2 | Keyboard controller |
| IC8, IC11 | 64K × 4 DRAM for the LCD controller | IC10 | MAX241 RS232 driver |
| IC24, IC25, IC32 | LM386 audio amplifiers | IC14 | 555 timer (BMU wake-up pulses) |
| IC1 | LM324 quad op-amp (battery sensing) | IC22 | DS2400 unique ID |
On the 4 MB board the first megabyte is two 256K × 16 SOJ DRAMs (IC29, IC37), the second is two 256K × 16 ZIP DRAMs (IC30, IC39) and the upper 2 MB is four 512K × 8 ZIP DRAMs (IC18, IC19, IC21, IC27). The RAM size switches must match what is fitted.[3] The extension ROM in IC38, in the "fifth column" ROM position, holds the power management software; LK1 sets its size.[3][1]
Display
The display is a monochrome transmissive VGA LCD (Acorn part 0913,002) with a backlight lamp, a backlight control board and two 20-way flat flexible cables to the main board (SK3 and SK4).[3] Theo Markettos identifies the panel as an Epson ECM-0557A, with a pin-compatible Sharp LCM-5498-22NAK fitted to some machines; the Sharp panels look grey when lit and the Epson ones slightly brown.[4] Brightness and contrast are set by two thumbwheels to the left of the screen, and a lid switch turns the display off when the lid is closed.[8][3]
Expansion
The only internal expansion is a bay behind the keyboard for the A4 Econet module (ALA66), which plugs into the 26-way connector PL3. Acorn asks that cards in the bay draw no more than 200 mA continuous and 400 mA peak at 5 V, and power down when not in use.[3] An external monitor plugs into the VGA socket, and an AT keyboard into the PS/2 socket.[5]
Power and battery
The external adaptor produces a dc supply of typically 25 V. Inside the A4 it is split into UMAIN, a 21 V supply that reaches a DC/DC converter board through the on/off switch, and UBATT, a switchable current source that charges the battery under the control of the BMU. When the adaptor is absent, the battery feeds the DC/DC converter. The BMU measures battery voltage, current and temperature, drives the five-segment LCD gauge on the front edge, and can switch the DC/DC converter off when the battery voltage gets too low.[3] Trickle charge is 60 to 70 mA and quick charge 320 to 380 mA.[3]
The pack is labelled "Nickel Cadmium Battery 14,4 V 1800 mAh".[1] Acorn gives eight to ten hours for a full charge, after which the adaptor drops to trickle charge, and says a charged pack self-discharges in about two months in the machine and three months out of it.[6]
The main board also carries B1, a 1.2 V 11 mAh NiCd cell soldered to the board, which keeps the clock and CMOS settings.[3] Owners report that this cell leaks, more often than not, and that it damages the board around it.[9][10] Remove it from any A4 that still has it; see Acorn A4 Maintenance Guide.
Known problems
- The surface-mount electrolytic capacitors on the main board leak, and the leakage causes freezes, failure to start and corrosion. A full recap is the usual first step on an A4 that has not been serviced.[10][11] See Acorn A4 Capacitor Guide.
- The board-mounted backup cell B1 leaks and corrodes the board around it.[9]
- Battery packs of this age are dead and often leaking. See Acorn A4 Maintenance Guide#Battery pack.
- The two flexible display cables and the keyboard membrane cables are fragile.[1][12]
- The original Conner 60 MB hard discs suffer from sticking heads.[9]
- The brightness and contrast knobs go missing; a 3D-printable replacement by Ian Jeffray is published under CC BY 4.0.[13]
The Acorn A4 Troubleshooting Guide covers each fault in detail.
Documentation
- Acorn A4 Technical Reference Manual: Acorn's hardware reference (0490,058), the engineering drawings, and the owner's Welcome Guide and Portable Guide.
- Acorn's A4 brochure (APP455) and the PCW review are on Chris's Acorns.[1]
Related pages
- Acorn A4 Maintenance Guide
- Acorn A4 Troubleshooting Guide
- Acorn A4 Capacitor Guide
- Acorn Archimedes A5000
- Battery Explosion, Capacitor or Corrosion Damage
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Whytehead, Chris. "Acorn A4", Chris's Acorns, The Centre for Computing History (retrieved 2026-10-01). Launched June 1992; models AKB62, AKB64, AKB66; carry case; Triumph Adler case; his AKB64: board 190,260 issue 1, ARM3 VY86C020-25FC at 24 MHz, MEMC1a, VIDC1a, Epson SMD-1000 floppy drive, Conner CP2064 63 MB hard disc, RISC OS 3.10 dated 30 April 1992; fragile display ribbon cables replaced to get the screen working; battery pack dead.
- ↑ 2.0 2.1 2.2 Acorn Computers, press release "Announcing Acorn's A4 Portable - '... a quart in a pint pot'", issued by Brian Salter, 1992. Text via Chris's Acorns. Two models (2 MB with floppy; 4 MB with 60 MB IDE hard disc), prices ex VAT and for education, 12 MIPS claim, volume shipment from September.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 Acorn Computers, Acorn A4 Technical Reference Manual, part no. 0490,058, issue 1, February 1993. Hosted on this wiki: Acorn A4 Technical Reference Manual. System description pp. 1-1 to 1-22; power supply system pp. 1-23 to 1-25; plugs, sockets, links and switches pp. 1-26 to 1-28; parts lists pp. 2-1 to 2-12; expansion bay Appendix B.
- ↑ 4.0 4.1 Markettos, Theo. "LCD panel data", Acorn A4 pages (retrieved 2026-10-01). Panels Epson ECM-0557A; Sharp LCM-5498-22NAK pin compatible, fitted to his Triumph Alder Walkstation "and probably other A4s"; passive matrix 9-inch 640 × 480 monochrome.
- ↑ 5.0 5.1 5.2 Acorn Computers, "The technical specification of the Acorn A4". Text via Chris's Acorns (retrieved 2026-10-01).
- ↑ 6.0 6.1 Acorn Computers, Acorn A4 Welcome Guide, 1992. Hosted on this wiki: File:Acorn A4 Welcome Guide.pdf. Using the keyboard pp. 33 to 39 (FN mode, mouse emulation); power considerations pp. 59 to 66 (battery safety p. 59, charging and self-discharge p. 60, battery LED states p. 61, low battery warning pp. 63, 64); switching off pp. 71, 72; if things go wrong pp. 73 to 75.
- ↑ Bell, Graham. "Acorn A4", Personal Computer World, vol. 15 no. 9, September 1992. Scan via Chris's Acorns. 9-inch LCD; just over 3 kg ready to go; 10-layer motherboard two-fifths the size of an A4 sheet; no FPA socket; criticism of the flaps, the exposed power switch and the grubby textured finish.
- ↑ Acorn Computers, Acorn A4 Portable Guide, 1992. Hosted on this wiki: File:Acorn A4 Portable Guide.pdf. Power problems p. 8; problems pp. 25 to 28; hardware information pp. 41 to 50 (front controls p. 42, power adaptor connector p. 50); cleaning pp. 51 to 53.
- ↑ 9.0 9.1 9.2 Wilson, Adam. "1992 Acorn A4 Laptop Repair, Restoration, & Modifications", Adam's Vintage Computer Restorations, September 2024 (retrieved 2026-10-01). Board-mounted NiCd cell and surface-mount electrolytics both leak; recap with C134 pads lost; CMOS reset with Delete held at power-on; Conner hard disc sticking; CF adapter and IDEFS expansion ROM; battery pack of twelve Varta 1.2 V 1.4 Ah sub-C NiCd cells with a thermal fuse and two thermistors.
- ↑ 10.0 10.1 "A4 Laptop No Display", stardot.org.uk forum thread, December 2016 to April 2017. RobC: lost configuration cured with
*CONFIGURE MONITORTYPE 5(LCD) or 4 (external SVGA); the board-soldered cell "can fail and leak (and more often than not does)"; take care with the flexible cables; random freezes cured by recapping and cleaning the board. vectorlight: most capacitors had leaked and some pads lifted; no +5 V from the DC/DC converter cured by replacing the charger; keyboard LEDs flashing once a second traced to a broken track at pin 4 of the 555 timer (RSTINHIB to the BMU); crackling from the right audio channel and short freezes. - ↑ "Several A4 repairs", stardot.org.uk forum thread, November 2022. IanJeffray: a full blind recap is the usual first step on a never-serviced A4, "the only machine where a full blind re-cap is a recommended course of action".
- ↑ Markettos, Theo. "Dismantling the A4 base as far as the motherboard", Acorn A4 pages, 2005 (retrieved 2026-10-01).
- ↑ Jeffray, Ian. "Acorn A4 laptop LCD knob", Thingiverse thing 4891969, June 2021, CC BY 4.0: replacement contrast and brightness knobs, "as these seem to go missing". Archived copy: archive.org/details/thingiverse-4891969.