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{{Infobox computer
{{Infobox computer
| name        = Acorn Archimedes A540
| name        = Acorn Archimedes A540
| image        = [[File:Acorn_Archimedes_A540.jpg|250px]]
| image        = [[File:Acorn_Archimedes_A540.jpg|260px|frameless]]
| caption      = Acorn Archimedes A540
| caption      = Archimedes A540 with colour monitor and keyboard
| manufacturer = Acorn Computers Ltd
| manufacturer = Acorn Computers Ltd
| type        = Personal Computer
| type        = Personal computer (three-box desktop)
| release date = June 1990
| release date = June 1990
| discontinued = 1992
| price        = £2,495 ex VAT, no monitor
| price        = £2,495 + VAT (1990)
| cpu          = ARM3 on a plug-in processor card
| cpu          = ARM3 @ 25-26 MHz (variants at 30 MHz, 33 MHz)
| memory      = 4 MB, expandable to 16 MB with three 4 MB RAM cards
| memory      = 4 MB RAM (expandable to 16 MB)
| storage      = 3.5" floppy drive; 100 MB SCSI hard disc on an Acorn SCSI podule
| storage      = 3.5" floppy drive (800 KB), 100 MB SCSI hard drive
| display      = Analogue RGB (VIDC1a); high-resolution mono on three BNC sockets
| sound        = 8-channel stereo, 8-bit
| sound        = 8 channels, stereo (VIDC1a)
| os          = RISC OS 2.01
| os          = RISC OS 2.01
| predecessor  = [[Acorn Archimedes A440]]
| predecessor  = [[Acorn Archimedes A440]]
| successor    = [[Acorn A5000]]
| successor    = [[Acorn Archimedes A5000]]
| model        = AKB50
}}
}}
<templatestyles src="Template:StyledTable/styles.css" />
The '''Acorn Archimedes A540''' was launched in June 1990 as the top model of the Archimedes range, at £2,495 ex VAT without a monitor. It had an ARM3 as standard and was the only Archimedes that could be expanded to 16 MB. It came with a SCSI podule and a 100 MB hard disc.<ref name="chris540">Whytehead, Chris. [https://chrisacorns.computinghistory.org.uk/Computers/A540.html "Acorn Archimedes A540"], Chris's Acorns, archived by The Centre for Computing History. Launch, price, RAM cards, SCSI podule, PSU fans, BNC sockets, backplane and motherboard part numbers, and two documented machines with measured figures.</ref>


The '''Acorn Archimedes A540''' was introduced in June 1990 as the flagship model of the Archimedes range. It was Acorn's first machine to be fitted with the ARM3 processor as standard, supporting up to 16 MB of RAM, and included higher speed SCSI and provision for connecting genlock devices.
The A540 has the same hardware as Acorn's R260 RISC iX workstation, without RISC iX installed.<ref name="chris540" /> Acorn documented it with the R200 series in the [[Acorn Archimedes 500 Series and R200 Series Service Manual]].<ref name="sm500">Acorn Computers Limited, ''Acorn Archimedes 500 series / Acorn R200 series Service Manual'', part number 0486,056, issue 2, June 1991. System description pp. 1-1 to 1-2; power supply p. 1-15; sockets and podule power p. 1-19; SCSI interface pp. 2-18 onwards; disassembly p. 3-2; fault diagnosis pp. 4-2 and 5-23 to 5-27; parts lists pp. 6-1 to 6-10. Hosted on this wiki: [[Acorn Archimedes 500 Series and R200 Series Service Manual]].</ref>


== Overview ==
== Processor ==


The A540 represented Acorn's response to the need for a high-performance workstation in the Archimedes range. It was an anticipated consequence of Acorn's Unix workstation development, offering the same general specification as Acorn's R260 Unix workstation (running RISC iX) but without built-in Ethernet support and running RISC OS 2 instead of Unix. At £2,495 plus VAT, it was positioned as the top-of-the-range model, substantially more expensive than other Archimedes computers but offering unprecedented performance for the platform.
The ARM3 is on a daughter card that plugs into PL3 on the main board.<ref name="sm500" /> Chris Whytehead's two A540s have an original 26 MHz card (VL86C020), which has no socket for the FPA10, and a 33 MHz card (VY86C020-35) with an FPA10 fitted. With ARMSi v4.0 they measure 14.14 and 16.8 MIPS.<ref name="chris540" />


The A540 hardware was essentially identical to the R260 except that RISC iX was not installed; it could be purchased separately and installed on an A540. The machine was designed to appeal to professional users, educational institutions requiring maximum performance, and as a potential Unix workstation.
=== FPA10 floating point accelerator ===


== Hardware Specifications ==
Acorn released the FPA10 in July 1993 for the A540, the A5000 and the R260, at £99 ex VAT. On the A540 it fits a socket on the processor card. Acorn gave its dissipation as 250 mW and its peak throughput as up to 5 MFLOPS at 26 MHz. Owners of early A540s and R260s might need a free modification to the processor card before fitting one, and RISC iX needs an extra driver.<ref name="prfpa">Acorn Computers Limited, press release "Acorn Releases Floating Point Accelerator", 5 July 1993. [https://chrisacorns.computinghistory.org.uk/docs/Acorn/PR/FPA_release.txt Text] via Chris's Acorns.</ref>


=== Processor ===
== Memory ==
The A540 featured an ARM3 processor on a replaceable CPU card. Initial models shipped with processors running at 25-26 MHz, though variants existed running at 30 MHz and 33 MHz. The 26 MHz version used a 52 MHz oscillator, while some machines used 60 MHz oscillators for 30 MHz operation. The ARM3 included 4 KB of cache memory, providing substantial performance improvements over ARM2-based models.


The CPU card could accommodate an FPA10 (Floating Point Accelerator), with FPA11 also being compatible with later variants. The 33 MHz ARM3 CPU with FPA10 combination represented the highest performance configuration available. The ceramic ARM3 processors used in some machines could be overclocked, with reports of stable operation at up to 40+ MHz.
A MEMC addresses at most 4 MB, so the A540 has a MEMC1a and 4 MB on the main board and three sockets, SK5, SK6 and SK7, for RAM cards that each carry their own MEMC1a and 4 MB. A machine therefore has 4, 8, 12 or 16 MB.<ref name="chris540" /><ref name="sm500" />


=== Memory System ===
The main board uses thirty-two 1M × 1 80 ns DRAMs in 20-pin ZIP packages, with the master MEMC1a at IC60. Each RAM card has eight 1M × 4 80 ns SOJ DRAMs and its MEMC1a at IC10. Acorn's parts list states that the MEMCs must be Acorn part number 2201,393 to get the right timing.<ref name="sm500" /> Chris Whytehead records a 12 MHz memory clock on both his A540s, and Acorn and Simtec both made RAM cards.<ref name="chris540" /> Acorn's parts lists give every MEMC1a in the machine as a 12 MHz part.<ref name="sm500" />
The A540 had 4 MB RAM by default but could be expanded to 16 MB with additional RAM cards, each with its own 4 MB RAM and MEMC1a memory controller. This unique multi-MEMC configuration allowed the A540 to exceed the 4 MB limitation of single-MEMC systems.  


The memory expansion was achieved through up to three additional RAM cards, giving possible configurations of 4 MB, 8 MB, 12 MB, or 16 MB total. Both Acorn and third-party manufacturers like Simtec produced RAM cards for the system. The memory cards were noted to be somewhat temperamental and liable to become dislodged if the machine wasn't used for extended periods.
Chris Whytehead finds the A540 temperamental after a period out of use, and the RAM cards liable to work loose.<ref name="chris540" />


=== Storage ===
== Video and sound ==
Unlike the rest of the Archimedes range, the A540 had a SCSI interface as standard, specifically using an NCR 53C90 or 53C90A controller. The machine shipped with a 100 MB SCSI hard disc, with the Acorn AKA31 or AKA32 SCSI interface providing both internal and external SCSI connectivity. The system retained the standard 800 KB double-density 3.5" floppy drive used across the Archimedes range.


=== Video System ===
The A540 uses the VIDC1a.<ref name="chris540" /> Acorn's parts list places it at IC64 and lists IC54 as a 74S00, but the fault-finding pages of the same manual refer to the VIDC as IC54.<ref name="sm500" /> The three BNC sockets on the rear panel, found only on the A540 and R260, are SK12 to SK14: high-resolution mono video (0.7 V into 75 ohms at a 96 MHz dot rate), vertical sync and horizontal sync.<ref name="chris540" /><ref name="sm500" /> Sound is eight channels, each with its own stereo position.<ref name="sm500" />
The A540 used the VIDC1a (Video Controller) chip and included three BNC connectors unique to the A540 and R260 models. The system supported various display modes with resolutions up to 1152×896 pixels and could display 256 colors from a palette of 4096. The memory access frequency was raised to 12 MHz in the A540, compared to 8 MHz in earlier models, providing enhanced system performance.


=== Power Supply and Cooling ===
== SCSI ==
The A540 featured a larger power supply than standard Archimedes machines, containing two fans for cooling. The system was noted to generate considerable heat, particularly with fully loaded configurations, and the memory cards were susceptible to heat-related issues.


=== Expansion ===
The A540's SCSI interface is a podule, not part of the main board, so one of the four slots is occupied from new.<ref name="chris540" /> Chris Whytehead's machines have the Acorn AKA31 (0173,010) and AKA32 Mk3 (0173,080).<ref name="chris540" /> Acorn's manual describes the card at component level: a Western Digital WD33C93A SCSI bus controller, an NEC μPD71071 DMA controller and 32K × 16 of static RAM.<ref name="sm500" />
The machine provided four podule (expansion card) slots, with all four remaining available for expansion since SCSI was integrated on the motherboard. The backplane supported various expansion cards including:
* Atomwide Ethernet IV cards for networking
* Computer Concepts Colour Card Gold for enhanced graphics
* Aleph1 386 PC emulation cards
* ScanLight podules for scanning
* MIDI interfaces


== Operating System ==
== Power supply and expansion ==


The A540 was launched with RISC OS 2.01, which included bug fixes and improvements over the earlier 2.00 release. The ROM-based operating system provided:
The power supply is larger than a standard Archimedes unit and has two fans.<ref name="chris540" /> Acorn's specification for it:<ref name="sm500" />
* ARM3 processor support with cache control
* Native SCSI device handling through the SCSI manager
* Support for memory configurations beyond 4 MB
* Improved printer driver stability and font manager fixes


Many A540s were later upgraded to RISC OS 3.10 or 3.11, with the Acorn Universal Boot system being a popular addition for enhanced functionality. Some machines, particularly ex-Acorn examples, retained RISC OS 2.01 with specialized software such as SJResearch Nexus Level 4 fileserver software for Econet networks.
{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''A540 power supply outputs (Acorn specification)'''
! Rail !! Minimum !! Nominal !! Maximum !! Current !! Ripple and noise
|-
| +5 V || 4.9 V || 5 V || 5.1 V || 1.5–12.2 A || 50 mV pk-pk
|-
| +12 V || 11.4 V || 12 V || 12.6 V || 0–3.2 A || 100 mV pk-pk
|-
| −5 V || −4.5 V || −5 V || −5.5 V || 0–0.3 A || 50 mV pk-pk
|}


== RISC iX Capability ==
Total output is 100 W continuous and 122 W surge. The +5 V over-voltage protection trips between 5.8 V and 7.0 V. The input is 198–264 V AC at 47–53 Hz, with a 98–132 V version as a manufacturing option.<ref name="sm500" />


While sold as a RISC OS machine, the A540 could run RISC iX (Acorn's BSD Unix variant) when purchased separately. The hardware provided genuine Unix workstation capabilities, supporting:
The backplane is Acorn part 0186,001 with four slots, and the main board is 0186,000.<ref name="chris540" /> Each podule slot may draw up to 1 A at +5 V, 250 mA at +12 V and 50 mA at −5 V.<ref name="sm500" /> Cards on Chris Whytehead's machines include an Atomwide Ethernet IV, a Computer Concepts Colour Card, a Computer Concepts ScanLight interface and an Aleph One 386 PC card.<ref name="chris540" />
* Multi-user operation via serial terminals
* X Windows System
* Standard Unix development tools
* Network operation via optional Ethernet cards


Performance under RISC iX was reported to be competitive with contemporary Unix workstations, with the ARM3's cache particularly benefiting Unix operations.
[[File:Acorn Archimedes A540 motherboard.jpg|thumb|360px|A540 with the backplane, processor card and RAM cards removed. The rear panel with its three BNC sockets is at the bottom.]]


== Technical Details ==
== Capacitors ==


=== Motherboard Revisions ===
Acorn's main board parts list mixes radial electrolytics, tantalums, ceramics and surface-mount decouplers in one C-number sequence. The polarised parts are:<ref name="sm500" />
The A540 motherboard existed in at least two documented versions:
* Issue 1: Initial production version
* Issue 2: Revised version with minor improvements


The motherboard design utilized PAL chips to alter addressing for each MEMC, enabling the multi-MEMC memory configuration. The system used different phases of the memory clock (derived from a 72 MHz oscillator) for each MEMC, with abort signals ANDed together so an abort only occurred if all MEMCs failed to translate an address.
{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''A540 polarised capacitors (Acorn parts lists, pp. 6-1, 6-2, 6-6 and 6-7)'''
! Board !! Designators !! Value and type
|-
| Main board || C1–C4, C186–C195 || 10 µF 10 V tantalum
|-
| Main board || C5, C6, C13, C19, C20, C21, C24, C27, C30, C35, C37 || 220 µF 16 V radial electrolytic
|-
| Main board || C7, C9, C16, C23, C26, C29, C33 || 47 µF 16 V radial electrolytic
|-
| Main board || C8, C14 || 4.7 µF 16 V radial electrolytic
|-
| Main board || C10, C15 || 1000 µF 25 V radial electrolytic
|-
| Main board || C11, C12, C18, C31, C34, C36 || 10 µF 16 V radial electrolytic
|-
| Main board || C17 || 100 µF 25 V radial electrolytic
|-
| 4 MB RAM card || C1–C4 || 47 µF surface-mount tantalum
|-
| Backplane || C4, C5, C6 || 47 µF 16 V axial electrolytic
|-
| ARM3 card || C1, C2 || 47 µF 10 V axial electrolytic
|}


== See Also ==
C22, C25, C28 and C32, in the middle of the electrolytic run, are 47 nF ceramics. Acorn's video fault procedure checks for +5 V at both ends of L1 and, if it is open, for C9 short-circuit.<ref name="sm500" />
* [[Acorn Archimedes A440]]
* [[Acorn A5000]]


== External Links ==
== Backup battery ==
* [http://chrisacorns.computinghistory.org.uk/Computers/A540.html Chris's Acorns: Acorn Archimedes A540]
 
* [http://www.computinghistory.org.uk/ Centre for Computing History]
The clock and CMOS RAM are backed by BT1, a 1.2 V 280 mAh NiCd cell soldered to the main board, with a foam pad beneath it.<ref name="sm500" /> It is a rechargeable cell, unlike the two AA alkaline cells of the A440 and the earlier machines.<ref name="sm440">Acorn Computers Limited, ''High Performance Computer Systems Model 440 Service Manual'', part number 0476,155, issue 1, November 1988, p. 6 (internal batteries). Hosted on this wiki: [[Archimedes 440 Service Manual]].</ref>
* [https://www.4corn.co.uk/archimedes.php 4corn Computers: The Acorn Archimedes]
 
Acorn's check: if the configuration memory loses its contents and the clock fails, measure IC22 pin 8 with the power off. It should be about 2.8 V; if not, check the charge state of BT1. If the PCF8583 at IC22 always fails on the same data bits, change it. If the clock stops or runs inaccurately, check crystal X3; LK8 gives access to the clock signal.<ref name="sm500" />
 
Old NiCd cells leak electrolyte that corrodes the tracks around them. Remove BT1 from a stored machine before powering it; see [[Battery Explosion, Capacitor or Corrosion Damage]] and [[Battery Refurbishment]].
 
== Operating system ==
 
The A540 shipped with RISC OS 2.01 (ROMs dated 5 July 1990). Chris Whytehead's first machine has been upgraded to RISC OS 3.11 with the Acorn Universal Boot; his second, from an ex-Acorn employee, still runs RISC OS 2.01 with SJ Research Nexus Level 4 Econet fileserver software.<ref name="chris540" /> The four RISC OS ROMs are IC47 to IC50.<ref name="sm500" />
 
== Serial port ==
 
The 500 and R200 series serial port follows RS232, unlike the RS423 port of the earlier Archimedes machines, and the RS423 Drive patch (version 1.24) used on those is not needed.<ref name="sm500" />
 
== Maintenance and repair ==
 
* Remove BT1 and inspect the board around it before powering a stored machine.
* Measure +5 V, +12 V and −5 V against the table above before chasing other faults.
* Reseat the RAM cards in SK5 to SK7 on a machine that is unstable or reports the wrong memory size.
* For a dead machine, Acorn's procedure swaps the processor card, MEMC IC60, IOC IC58 and the VIDC in turn, then checks the 24 MHz system clock at LK11 and the 96 MHz oscillator at IC57.<ref name="sm500" />
* Check that both power supply fans turn.
* If an FPA10 does not work in an early machine, the processor card may need Acorn's modification.<ref name="prfpa" />
* Acorn's SCSI drive test reformats the disc and destroys its data.<ref name="sm500" /> See [[Hard Drive Maintenance and Repair]] and, for the Citizen OSDC-65C floppy drive on Chris Whytehead's machines,<ref name="chris540" /> [[Floppy Drive Repair]].
 
Acorn's manual treats the power supply as a replaceable module with no user-serviceable parts and gives no component list for it.<ref name="sm500" />
 
== Documentation ==
 
* [[Acorn Archimedes 500 Series and R200 Series Service Manual]]: part 0486,056, issue 2, June 1991. System description, interface cards, disassembly, functional tests, component-level fault finding and parts lists for the main board, RAM card, backplane, ARM3 card, keyboard, Ethernet and SCSI cards.
 
== See also ==
 
* [[Acorn Archimedes A440]], the 1987 top model it replaced
* [[Acorn Archimedes A410]] and [[Acorn Archimedes A420]], the 400/1 range
* [[Acorn Archimedes A5000]], the 1991 ARM3 machine
 
== References ==
 
<references />
 
{{Navbox-AcornComputers|state=collapsed}}


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

Latest revision as of 07:45, 1 October 2026

Acorn Archimedes A540
Archimedes A540 with colour monitor and keyboard
Specifications
ManufacturerAcorn Computers Ltd
TypePersonal computer (three-box desktop)
ReleasedJune 1990
Intro price£2,495 ex VAT, no monitor
CPUARM3 on a plug-in processor card
Memory4 MB, expandable to 16 MB with three 4 MB RAM cards
Storage3.5" floppy drive; 100 MB SCSI hard disc on an Acorn SCSI podule
DisplayAnalogue RGB (VIDC1a); high-resolution mono on three BNC sockets
Sound8 channels, stereo (VIDC1a)
OS / FirmwareRISC OS 2.01
PredecessorAcorn Archimedes A440
SuccessorAcorn Archimedes A5000
Model no.AKB50

The Acorn Archimedes A540 was launched in June 1990 as the top model of the Archimedes range, at £2,495 ex VAT without a monitor. It had an ARM3 as standard and was the only Archimedes that could be expanded to 16 MB. It came with a SCSI podule and a 100 MB hard disc.[1]

The A540 has the same hardware as Acorn's R260 RISC iX workstation, without RISC iX installed.[1] Acorn documented it with the R200 series in the Acorn Archimedes 500 Series and R200 Series Service Manual.[2]

Processor

[edit | edit source]

The ARM3 is on a daughter card that plugs into PL3 on the main board.[2] Chris Whytehead's two A540s have an original 26 MHz card (VL86C020), which has no socket for the FPA10, and a 33 MHz card (VY86C020-35) with an FPA10 fitted. With ARMSi v4.0 they measure 14.14 and 16.8 MIPS.[1]

FPA10 floating point accelerator

[edit | edit source]

Acorn released the FPA10 in July 1993 for the A540, the A5000 and the R260, at £99 ex VAT. On the A540 it fits a socket on the processor card. Acorn gave its dissipation as 250 mW and its peak throughput as up to 5 MFLOPS at 26 MHz. Owners of early A540s and R260s might need a free modification to the processor card before fitting one, and RISC iX needs an extra driver.[3]

Memory

[edit | edit source]

A MEMC addresses at most 4 MB, so the A540 has a MEMC1a and 4 MB on the main board and three sockets, SK5, SK6 and SK7, for RAM cards that each carry their own MEMC1a and 4 MB. A machine therefore has 4, 8, 12 or 16 MB.[1][2]

The main board uses thirty-two 1M × 1 80 ns DRAMs in 20-pin ZIP packages, with the master MEMC1a at IC60. Each RAM card has eight 1M × 4 80 ns SOJ DRAMs and its MEMC1a at IC10. Acorn's parts list states that the MEMCs must be Acorn part number 2201,393 to get the right timing.[2] Chris Whytehead records a 12 MHz memory clock on both his A540s, and Acorn and Simtec both made RAM cards.[1] Acorn's parts lists give every MEMC1a in the machine as a 12 MHz part.[2]

Chris Whytehead finds the A540 temperamental after a period out of use, and the RAM cards liable to work loose.[1]

Video and sound

[edit | edit source]

The A540 uses the VIDC1a.[1] Acorn's parts list places it at IC64 and lists IC54 as a 74S00, but the fault-finding pages of the same manual refer to the VIDC as IC54.[2] The three BNC sockets on the rear panel, found only on the A540 and R260, are SK12 to SK14: high-resolution mono video (0.7 V into 75 ohms at a 96 MHz dot rate), vertical sync and horizontal sync.[1][2] Sound is eight channels, each with its own stereo position.[2]

SCSI

[edit | edit source]

The A540's SCSI interface is a podule, not part of the main board, so one of the four slots is occupied from new.[1] Chris Whytehead's machines have the Acorn AKA31 (0173,010) and AKA32 Mk3 (0173,080).[1] Acorn's manual describes the card at component level: a Western Digital WD33C93A SCSI bus controller, an NEC μPD71071 DMA controller and 32K × 16 of static RAM.[2]

Power supply and expansion

[edit | edit source]

The power supply is larger than a standard Archimedes unit and has two fans.[1] Acorn's specification for it:[2]

A540 power supply outputs (Acorn specification)
Rail Minimum Nominal Maximum Current Ripple and noise
+5 V 4.9 V 5 V 5.1 V 1.5–12.2 A 50 mV pk-pk
+12 V 11.4 V 12 V 12.6 V 0–3.2 A 100 mV pk-pk
−5 V −4.5 V −5 V −5.5 V 0–0.3 A 50 mV pk-pk

Total output is 100 W continuous and 122 W surge. The +5 V over-voltage protection trips between 5.8 V and 7.0 V. The input is 198–264 V AC at 47–53 Hz, with a 98–132 V version as a manufacturing option.[2]

The backplane is Acorn part 0186,001 with four slots, and the main board is 0186,000.[1] Each podule slot may draw up to 1 A at +5 V, 250 mA at +12 V and 50 mA at −5 V.[2] Cards on Chris Whytehead's machines include an Atomwide Ethernet IV, a Computer Concepts Colour Card, a Computer Concepts ScanLight interface and an Aleph One 386 PC card.[1]

A540 with the backplane, processor card and RAM cards removed. The rear panel with its three BNC sockets is at the bottom.

Capacitors

[edit | edit source]

Acorn's main board parts list mixes radial electrolytics, tantalums, ceramics and surface-mount decouplers in one C-number sequence. The polarised parts are:[2]

A540 polarised capacitors (Acorn parts lists, pp. 6-1, 6-2, 6-6 and 6-7)
Board Designators Value and type
Main board C1–C4, C186–C195 10 µF 10 V tantalum
Main board C5, C6, C13, C19, C20, C21, C24, C27, C30, C35, C37 220 µF 16 V radial electrolytic
Main board C7, C9, C16, C23, C26, C29, C33 47 µF 16 V radial electrolytic
Main board C8, C14 4.7 µF 16 V radial electrolytic
Main board C10, C15 1000 µF 25 V radial electrolytic
Main board C11, C12, C18, C31, C34, C36 10 µF 16 V radial electrolytic
Main board C17 100 µF 25 V radial electrolytic
4 MB RAM card C1–C4 47 µF surface-mount tantalum
Backplane C4, C5, C6 47 µF 16 V axial electrolytic
ARM3 card C1, C2 47 µF 10 V axial electrolytic

C22, C25, C28 and C32, in the middle of the electrolytic run, are 47 nF ceramics. Acorn's video fault procedure checks for +5 V at both ends of L1 and, if it is open, for C9 short-circuit.[2]

Backup battery

[edit | edit source]

The clock and CMOS RAM are backed by BT1, a 1.2 V 280 mAh NiCd cell soldered to the main board, with a foam pad beneath it.[2] It is a rechargeable cell, unlike the two AA alkaline cells of the A440 and the earlier machines.[4]

Acorn's check: if the configuration memory loses its contents and the clock fails, measure IC22 pin 8 with the power off. It should be about 2.8 V; if not, check the charge state of BT1. If the PCF8583 at IC22 always fails on the same data bits, change it. If the clock stops or runs inaccurately, check crystal X3; LK8 gives access to the clock signal.[2]

Old NiCd cells leak electrolyte that corrodes the tracks around them. Remove BT1 from a stored machine before powering it; see Battery Explosion, Capacitor or Corrosion Damage and Battery Refurbishment.

Operating system

[edit | edit source]

The A540 shipped with RISC OS 2.01 (ROMs dated 5 July 1990). Chris Whytehead's first machine has been upgraded to RISC OS 3.11 with the Acorn Universal Boot; his second, from an ex-Acorn employee, still runs RISC OS 2.01 with SJ Research Nexus Level 4 Econet fileserver software.[1] The four RISC OS ROMs are IC47 to IC50.[2]

Serial port

[edit | edit source]

The 500 and R200 series serial port follows RS232, unlike the RS423 port of the earlier Archimedes machines, and the RS423 Drive patch (version 1.24) used on those is not needed.[2]

Maintenance and repair

[edit | edit source]
  • Remove BT1 and inspect the board around it before powering a stored machine.
  • Measure +5 V, +12 V and −5 V against the table above before chasing other faults.
  • Reseat the RAM cards in SK5 to SK7 on a machine that is unstable or reports the wrong memory size.
  • For a dead machine, Acorn's procedure swaps the processor card, MEMC IC60, IOC IC58 and the VIDC in turn, then checks the 24 MHz system clock at LK11 and the 96 MHz oscillator at IC57.[2]
  • Check that both power supply fans turn.
  • If an FPA10 does not work in an early machine, the processor card may need Acorn's modification.[3]
  • Acorn's SCSI drive test reformats the disc and destroys its data.[2] See Hard Drive Maintenance and Repair and, for the Citizen OSDC-65C floppy drive on Chris Whytehead's machines,[1] Floppy Drive Repair.

Acorn's manual treats the power supply as a replaceable module with no user-serviceable parts and gives no component list for it.[2]

Documentation

[edit | edit source]
  • Acorn Archimedes 500 Series and R200 Series Service Manual: part 0486,056, issue 2, June 1991. System description, interface cards, disassembly, functional tests, component-level fault finding and parts lists for the main board, RAM card, backplane, ARM3 card, keyboard, Ethernet and SCSI cards.

See also

[edit | edit source]

References

[edit | edit source]
  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 Whytehead, Chris. "Acorn Archimedes A540", Chris's Acorns, archived by The Centre for Computing History. Launch, price, RAM cards, SCSI podule, PSU fans, BNC sockets, backplane and motherboard part numbers, and two documented machines with measured figures.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 Acorn Computers Limited, Acorn Archimedes 500 series / Acorn R200 series Service Manual, part number 0486,056, issue 2, June 1991. System description pp. 1-1 to 1-2; power supply p. 1-15; sockets and podule power p. 1-19; SCSI interface pp. 2-18 onwards; disassembly p. 3-2; fault diagnosis pp. 4-2 and 5-23 to 5-27; parts lists pp. 6-1 to 6-10. Hosted on this wiki: Acorn Archimedes 500 Series and R200 Series Service Manual.
  3. ↑ 3.0 3.1 Acorn Computers Limited, press release "Acorn Releases Floating Point Accelerator", 5 July 1993. Text via Chris's Acorns.
  4. ↑ Acorn Computers Limited, High Performance Computer Systems Model 440 Service Manual, part number 0476,155, issue 1, November 1988, p. 6 (internal batteries). Hosted on this wiki: Archimedes 440 Service Manual.


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