Editing Acorn Archimedes A4000

{{Infobox computer
| name         = Acorn Archimedes A4000
| image        = [[File:Acorn_Archimedes_A4000.jpg|250px]]
| caption      = Acorn Archimedes A4000
| manufacturer = Acorn Computers Ltd
| type         = Personal computer (three-box desktop)
| release date = September 1992
| discontinued = 1995
| price        = £949 ex VAT (2 MB, 80 MB hard disc, with monitor)
| cpu          = ARM250 @ 12 MHz
| memory       = 2 MB RAM (expandable to 4 MB)
| storage      = 3.5" floppy (1.6 MB); 3.5" IDE hard disc (80/105/210 MB)
| display      = Analogue RGB, 15-pin VGA-type connector
| sound        = 8-channel, 8-bit logarithmic (VIDC1a)
| dimensions   = approx. 430 mm × 340 mm × 95 mm
| weight       = approx. 6 kg
| os           = RISC OS 3.11
| predecessor  = [[Acorn Archimedes A3000]]
| successor    = [[Acorn A7000]]
| codename     = Roadrunner
| model        = AGC10–AGC82
}}
The '''Acorn Archimedes A4000''' is a three-box desktop computer that [[Acorn Computers]] announced in August 1992 and shipped from September 1992. It was the "professional" member of a three-machine range built around the ARM250 processor, sold alongside the home-market [[Acorn Archimedes A3010|A3010]] and the education [[Acorn Archimedes A3020|A3020]].<ref name="chris">Whytehead, Chris. [https://chrisacorns.computinghistory.org.uk/Computers/A4000.html "Acorn A4000"], Chris's Acorns / The Centre for Computing History.</ref><ref name="arcwiki">[https://arcwiki.org.uk/index.php/A4000 "A4000"], Arc Wiki.</ref>

Where the A3010 and A3020 built the computer into a keyboard case, the A4000 put the same design into a slimline desktop box with a separate keyboard. Its specification is almost identical to the A3020; the practical difference is a 3.5-inch IDE hard disc in place of the A3020's 2.5-inch drive.<ref name="chris" /><ref name="arcwiki" />

== Positioning ==

Acorn sold the A4000 as a "professional 3-box solution" for home-office and business use, above the home [[Acorn Archimedes A3010|A3010]] and the education [[Acorn Archimedes A3020|A3020]] but below the ARM3-based [[Acorn Archimedes A5000|A5000]].<ref name="chris" /> It shipped in a beige slimline case with a detachable 103-key keyboard and a three-button mouse.<ref name="classic">[http://classicacorn.computinghistory.org.uk/32bit_machine_spec/a4000_spec/a4000_spec.html "A4000 Specifications"], ClassicAcorn.</ref> Acorn sold it in several bundles — Home Office, Learning Curve and Early Years — with model codes from AGC10 to AGC82.<ref name="chris" /><ref name="arcwiki" />

The launch price, quoted with an 80 MB hard disc and a colour monitor and excluding VAT, was £949.<ref name="arcwiki" />

== Processor ==

The A4000 uses the '''ARM250''' at 12 MHz, the single-chip device that integrates an ARM2-class core, the MEMC1a memory controller, the VIDC1a video and sound controller, and the IOC input/output controller.<ref name="wp">[https://en.wikipedia.org/wiki/Acorn_Archimedes "Acorn Archimedes"], Wikipedia.</ref> (Some period Acorn material lists the integrated I/O part as "IOMD"; that is a later Risc PC chip, and the ARM250 integrates the IOC.)<ref name="wp" /><ref name="chris" /> Two A4000s measured for Chris's Acorns returned about 7.19 and 7.61 MIPS on the ARMSi benchmark, and roughly 5,400–5,600 Dhrystones per second, which is in line with the 12 MHz ARM250 in the A3020.<ref name="chris" />

A Chips & Technologies 82C711 peripheral controller provides the IDE, floppy, serial and parallel interfaces in a single support chip.<ref name="82c711">[https://arcwiki.org.uk/index.php/82C711 "82C711"], Arc Wiki.</ref>

== Memory and firmware ==

The A4000 ships with 2 MB of RAM. It is expanded to a 4 MB maximum with a plug-in RAM upgrade board (for example the Simtec unit) that fits over the on-board memory — the motherboard carries the base memory with sockets for the expansion cards, not standard PC SIMMs.<ref name="chris" /><ref name="arcwiki" /> RISC OS is held in 2 MB of ROM (two devices); production machines carry RISC OS 3.11, dated 29 September 1992.<ref name="chris" />

== Storage ==

The floppy drive is a 3.5-inch high-density unit formatted to 1.6 MB, driven by the 82C711.<ref name="classic" /> Unlike the A3020's 2.5-inch drive, the A4000 fits a '''3.5-inch IDE hard disc''' through the same on-board IDE interface. Documented drives are 80 MB, 105 MB (Conner CFS105A) and 210 MB (Conner CFS210A), depending on model.<ref name="chris" /><ref name="arcwiki" />

== Ports and expansion ==

The rear panel carries, from left to right, the keyboard socket, a parallel printer port, a serial (RS232) port, an Econet socket (usually not fitted), a headphone socket and the analogue RGB video output, with the separate power supply at the left of the panel.<ref name="chris" /> The video connector is a 15-pin VGA-style socket carrying analogue RGB.<ref name="classic" />

Internally the A4000 has one mini-podule expansion slot, the same single-slot arrangement as the A3010 and A3020, plus a network-interface slot for an Econet or Ethernet module.<ref name="chris" /><ref name="classic" /> Common additions were an Ethernet mini-podule and a RAM upgrade board.<ref name="chris" />

== Case and power ==

The A4000 is a slimline three-box desktop: system unit, separate keyboard and monitor. The case has two 3.5-inch drive bays, one of them accessible from the front for the floppy drive.<ref name="arcwiki" /> Unlike the A3010 and A3020, whose power supply is built onto the main board, the A4000 has a '''separate cased mains power-supply module''' that Acorn treats as a replaceable service part.<ref name="sm">[[Acorn A3010, A3020 and A4000 Service Manual]], Acorn Computers Ltd — hosted on this wiki.</ref> The machine is unusually simple to open: two screws release the cover, after which the board and drives lift out.<ref name="chris" />

== Differences from the A3010 and A3020 ==

All three 1992 machines share essentially the same "Roadrunner"-family main-board design.<ref name="wp" /> The A4000 differs as follows:

{| class="wikitable styled-table" style="width:90%; text-align:left;"
! Feature !! A4000 (professional) !! A3020 (education) !! A3010 (home)
|-
| Form factor || Three box, separate keyboard || Single box, integral keyboard || Single box, integral keyboard
|-
| Hard disc || On-board IDE, 3.5" drive standard || On-board IDE, optional 2.5" drive || None fitted
|-
| Network socket || Yes || Yes || No
|-
| TV modulator || No || No || Yes
|-
| Joystick ports || No || No || Two (9-pin)
|-
| Power supply || Separate cased module || On-board || On-board
|}

Sources: Chris's Acorns and Wikipedia.<ref name="chris" /><ref name="wp" />

== Circuit diagrams and PCB ==

The A4000 main board is part 0194,600, codenamed "Roadrunner". Acorn documented the machine at module level in the [[Acorn A3010, A3020 and A4000 Service Manual|Service Manual]]; the component-level circuit diagrams are in the [[Acorn A3010, A3020 and A4000 Technical Reference Manual|Technical Reference Manual]], both hosted on this wiki.

{| class="wikitable styled-table" style="width:80%; text-align:center;"
! Main PCB !! Circuit diagram (sheet 1 of 3)
|-
| [[File:Acorn Archimedes A4000 motherboard.jpg|400px]] || [[File:Acorn Archimedes A4000 circuit diagram (1 of 3).png|400px]]
|-
! Circuit diagram (sheet 2 of 3) !! Circuit diagram (sheet 3 of 3)
|-
| [[File:Acorn Archimedes A4000 circuit diagram (2 of 3).png|400px]] || [[File:Acorn Archimedes A4000 circuit diagram (3 of 3).png|400px]]
|}

== Discontinuation ==

Acorn ceased A4000 production in 1995, with remaining stock sold into 1996; along with the A3020 it did not conform to newly introduced European electrical regulations.<ref name="wp" /><ref name="arcwiki" /> The [[Acorn Risc PC 600|Acorn Risc PC]] took over as Acorn's desktop from 1994, and the entry-level role passed to the Acorn A7000.

== General maintenance ==
{{Main|Acorn Archimedes A4000 Maintenance Guide}}

The main maintenance jobs are the soldered NiCd backup battery, which leaks and corrodes the board around it, the separate mains PSU module, and the ageing IDE hard disc. See the [[Acorn Archimedes A4000 Maintenance Guide]].

== Troubleshooting ==
{{Main|Acorn Archimedes A4000 Troubleshooting Guide}}

Common faults are battery corrosion, PSU-module failure, hard-disc failure, and no-picture symptoms caused by a monitor-type mismatch. Because the ARM250 integrates the processor, memory, video and I/O controllers, a fault inside it is a whole-device replacement. See the [[Acorn Archimedes A4000 Troubleshooting Guide]].

== Capacitor guide ==
{{Main|Acorn Archimedes A4000 Capacitor Guide}}

The A4000 board uses conventional leaded electrolytics with surface-mount ceramic decouplers and is not affected by the surface-mount electrolyte leakage of the [[Acorn Archimedes A5000|A5000]], A4 laptop and Risc PC; the recap priority is the separate PSU module. See the [[Acorn Archimedes A4000 Capacitor Guide]].

== See also ==

* [[Acorn Archimedes A3020]] — education sibling (same board, 2.5" drive)
* [[Acorn Archimedes A3010]] — home-market sibling
* [[Acorn Archimedes A3000]] — predecessor
* [[Acorn Archimedes A5000]] — ARM3 flagship of the same era

== References ==

<references />

{{Navbox-AcornComputers}}

[[Category:Acorn Computers]]
[[Category:1992 Computers]]