Editing Acorn Archimedes A5000

{{Infobox computer
| name         = Acorn Archimedes A5000
| image        = [[File:Acorn Archimedes A5000 open.jpg|250px]]
| caption      = Acorn Archimedes A5000
| manufacturer = Acorn Computers Ltd
| type         = Personal Computer
| release date = September 1991
| discontinued = 1993
| price        = £1,499 (2 MB), £1,999 (4 MB)
| cpu          = ARM3 @ 25 MHz
| memory       = 2 MB or 4 MB RAM (expandable to 8 MB)
| storage      = 3.5" floppy drive (1.6 MB), 40/80/120 MB IDE hard drive
| display      = 640×480 (256 colours), 800×600 (256 colours), 1024×768 (16 colours)
| sound        = 8-channel stereo, 8-bit logarithmic DAC
| dimensions   = 420 mm × 340 mm × 105 mm
| weight       = 8.5 kg
| os           = RISC OS 3.00
| predecessor  = [[Acorn Archimedes A540]], [[Acorn Archimedes A420]]
| successor    = [[Acorn Risc PC]]
| codename     = 
| model        = 
}}

The '''Acorn Archimedes A5000''' was released in September 1991 as a mid-range professional computer, bridging the gap between the entry-level A3000 series and the high-end A540. Featuring the ARM3 processor at 25 MHz with integrated cache, the A5000 combined workstation-class performance with affordability, becoming one of Acorn's most successful second-generation Archimedes models.

== Overview ==

The A5000 addressed market demands for ARM3 performance without the A540's premium pricing. By utilizing IDE storage instead of SCSI and limiting maximum RAM to 8 MB, Acorn reduced costs while maintaining professional capabilities. The machine targeted educational establishments, small businesses, and power users who required more performance than the A3000 series but could not justify the A540's expense.

Acorn offered multiple configurations to suit different markets. The base model with 2 MB RAM and 40 MB hard drive competed with high-end PCs, while the 4 MB/120 MB configuration challenged entry-level workstations. The inclusion of RISC OS 3.00 marked a significant advancement in the operating system, introducing cooperative multitasking improvements and enhanced desktop functionality.

== Architecture ==

The A5000 utilized a refined architecture combining proven components with cost-effective design choices. The ARM3 processor provided the performance foundation, while careful system integration minimized component count and manufacturing costs.

=== System Design ===

{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Component !! Implementation !! Function
|-
| ARM3 || 25 MHz, 4 KB cache || Central processor
|-
| MEMC1a || Single chip || Memory controller, DMA
|-
| VIDC1a/VIDC20 || Enhanced timing || Video and sound
|-
| IOC || Standard implementation || I/O control, timers
|-
| COMBO chip || 82C711 || IDE, floppy, serial, parallel
|}

The integration of multiple I/O functions into the 82C711 COMBO chip reduced board complexity and cost. This chip handled IDE and floppy disk control, serial and parallel ports, and real-time clock functions, eliminating several discrete components used in earlier designs.

=== Memory Architecture ===

The A5000's memory system balanced performance with cost:

{| class="wikitable styled-table" style="width:85%; text-align:center;"
! Configuration !! SIMM Type !! Slots Used !! Total RAM !! Expansion Path
|-
| 2 MB model || 2× 1MB 30-pin || 2 of 4 || 2 MB || Add 2 SIMMs
|-
| 4 MB model || 4× 1MB 30-pin || 4 of 4 || 4 MB || Replace all
|-
| 8 MB upgrade || 4× 2MB 30-pin || 4 of 4 || 8 MB || Maximum
|}

The use of industry-standard 30-pin SIMMs reduced memory costs compared to proprietary modules. The MEMC1a controller supported up to 8 MB directly, though RISC OS could only utilize 8 MB total including VRAM.

== Hardware Specifications ==

The A5000 motherboard represented mature Archimedes design, incorporating lessons from five years of production experience.

=== Processor Subsystem ===

The ARM3 processor configuration:
* '''Clock frequency:''' 25 MHz from 50 MHz crystal
* '''Cache:''' 4 KB unified instruction/data
* '''Cache organization:''' 64 lines of 16 words
* '''Cache timing:''' Single-cycle hit, 4-cycle miss
* '''Write strategy:''' Write-through
* '''Power consumption:''' 1.4W typical

The cache provided approximately 85% hit rate for typical applications, reducing memory bandwidth requirements substantially. This proved crucial given the memory system's shared bandwidth with video and sound DMA.

=== IDE Storage System ===

{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Specification !! Details !! Performance
|-
| Controller || 82C711 COMBO chip || PIO Mode 2
|-
| Interface || 40-pin IDE connector || 16-bit data path
|-
| Transfer rate || 3.3 MB/s maximum || 1.5 MB/s typical
|-
| Drive options || 40/80/120 MB || Various manufacturers
|-
| File system || RISC OS 3 ADFS || Long filenames, 512 MB limit
|}

Common drive configurations:
* '''40 MB:''' Conner CP3044 or Western Digital WD93044
* '''80 MB:''' Conner CP3084 or Maxtor 7080A
* '''120 MB:''' Conner CP30124 or Seagate ST3144A

The IDE interface's simplicity improved reliability compared to SCSI, though with reduced performance and expandability.

== Video Capabilities ==

The A5000 shipped with either VIDC1a or VIDC20 depending on production date:

=== Video Controller Comparison ===

{| class="wikitable styled-table" style="width:85%; text-align:center;"
! Feature !! VIDC1a (early units) !! VIDC20 (late units)
|-
| Maximum colors || 256 from 4096 || 256 from 16.7M
|-
| Resolutions || Fixed modes || Flexible timing
|-
| Pixel clock || 24 MHz || 36 MHz
|-
| VRAM support || No || Yes (1 MB)
|-
| Hardware cursor || 32×32×3 colors || 32×32×3 colors
|}

VIDC20-equipped machines could utilize 1 MB of VRAM for enhanced performance in high-resolution modes, though this option was rarely fitted due to cost.

=== Display Modes ===

{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Mode !! Resolution !! Colors !! Refresh !! Memory Used
|-
| 12 || 640×256 || 16 || 50 Hz || 80 KB
|-
| 13 || 640×256 || 256 || 50 Hz || 160 KB
|-
| 20 || 640×480 || 16 || 60 Hz || 150 KB
|-
| 21 || 640×480 || 256 || 60 Hz || 300 KB
|-
| 24 || 800×600 || 16 || 56 Hz || 234 KB
|-
| 27 || 640×480 || 256 || 70 Hz || 300 KB
|-
| 28 || 800×600 || 256 || 56 Hz || 468 KB
|}

The VGA-compatible modes (20, 21, 27) enabled use of standard PC monitors, significantly reducing total system cost compared to earlier models requiring expensive multisync displays.

== RISC OS 3.00 ==

The A5000 introduced RISC OS 3.00, a major operating system upgrade:

=== New Features ===

System improvements included:
* '''Application tasks:''' Improved cooperative multitasking
* '''Drag and drop:''' System-wide protocol for data transfer
* '''Outline fonts:''' Scalable font technology
* '''3D look:''' Enhanced desktop appearance
* '''Pinboard:''' Desktop background with file shortcuts
* '''Configuration:''' Non-volatile settings storage

Bundled applications:
* '''Edit:''' Enhanced text editor
* '''Paint:''' Improved bitmap editor
* '''Draw:''' Vector graphics with bezier curves
* '''Maestro:''' Music composition
* '''Alarm:''' Calendar and scheduling
* '''Chars:''' Character map utility

=== Memory Management ===

{| class="wikitable styled-table" style="width:85%; text-align:center;"
! Memory Area !! 2 MB System !! 4 MB System !! Purpose
|-
| Screen memory || 160-300 KB || 160-468 KB || Display buffer
|-
| System heap || 256 KB || 384 KB || OS workspace
|-
| Module area || 384 KB || 640 KB || Relocatable modules
|-
| Font cache || 128 KB || 256 KB || Outline fonts
|-
| Application space || 800 KB || 2 MB || User programs
|}

The improved memory management allowed multiple applications to coexist more effectively than RISC OS 2, though true preemptive multitasking remained absent.

== Expansion Options ==

The A5000 provided four podule expansion slots:

=== Common Expansion Cards ===

Popular expansions included:
* '''SCSI cards:''' Lingenuity, Morley, Oak Solutions
* '''Ethernet:''' i-cubed EtherLan 200/500
* '''Sound samplers:''' Wild Vision AudioDynamics
* '''MIDI interfaces:''' EMR Studio 24
* '''PC emulators:''' Aleph One 486 card
* '''Video digitizers:''' HCCS Vision

The four-slot capacity matched the A540, providing professional expansion capabilities at lower cost.

=== Network Options ===

{| class="wikitable styled-table" style="width:85%; text-align:center;"
! Interface !! Speed !! Protocol !! Typical Use
|-
| Econet (module) || 250 kbps || Proprietary || Educational networks
|-
| Ethernet (podule) || 10 Mbps || TCP/IP || Professional networks
|-
| Serial SLIP || 115.2 kbps || TCP/IP || Internet dial-up
|-
| Parallel PLIP || 50 KB/s || TCP/IP || Direct connection
|}

Ethernet gradually replaced Econet in educational settings, providing standard networking compatibility and improved performance.

== Software Ecosystem ==

The A5000's performance enabled sophisticated applications:

=== Professional Software ===

Key applications included:
* '''Impression Publisher:''' Professional desktop publishing
* '''Artworks:''' Vector illustration program
* '''ProArtisan 2:''' 24-bit image processing
* '''Sibelius 6:''' Music notation and MIDI
* '''Schema II:''' Electronic CAD
* '''Eureka 3:''' Mathematical solver

These applications leveraged the ARM3's performance for tasks previously requiring dedicated workstations.

=== Development Tools ===

Programming environments:
* '''Acorn C/C++:''' ANSI C and C++ compilers
* '''BBC BASIC V:''' Integrated interpreter/compiler
* '''Desktop Development Environment:''' Integrated development
* '''GCC:''' GNU compiler collection port
* '''StrongED:''' Programmer's editor

The 25 MHz ARM3 provided compilation speeds competitive with contemporary Unix workstations, attracting software developers.

== Performance Characteristics ==

The A5000 delivered impressive performance for its price point:

=== Benchmark Results ===

{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Test !! A5000 (25 MHz) !! A3020 (12 MHz) !! 486DX-33 !! Mac IIci
|-
| Dhrystone 2.1 || 20,000 || 5,400 || 16,000 || 11,000
|-
| Screen redraw || 320 ms || 1,200 ms || 450 ms || 380 ms
|-
| BASIC loop || 0.35 sec || 1.2 sec || N/A || N/A
|-
| File copy (HD) || 1.4 MB/s || N/A || 1.8 MB/s || 1.2 MB/s
|}

The ARM3 cache provided substantial benefits, with cache-friendly code running 4-5 times faster than ARM2 systems at equivalent clock speeds.

== Manufacturing History ==

Production evolved through several phases:

{| class="wikitable styled-table" style="width:85%; text-align:center;"
! Period !! Changes !! Drive Options !! Notes
|-
| Sep 1991-Mar 1992 || Initial release || 40/80 MB || VIDC1a
|-
| Apr-Sep 1992 || Component updates || 80/120 MB || Some VIDC20
|-
| Oct 1992-Mar 1993 || Cost reduction || 80/120 MB || VIDC20 standard
|-
| Apr-Dec 1993 || Final production || 120 MB only || Clearance sales
|}

Approximately 25,000 units were manufactured, making the A5000 one of Acorn's more successful professional models. Educational purchases accounted for 60% of sales, with the remainder split between business and advanced home users.

== Typical Configurations ==

The A5000 served various roles:

=== Educational Workstation ===

Standard classroom configuration:
* '''A5000 2 MB/40 MB''' base system
* '''4 MB RAM upgrade''' for multitasking
* '''Econet interface''' for network boot
* '''Shared printer''' via network
* '''Educational software''' suite

Schools often purchased class sets, with one A5000 serving as file server for A3010/A3020 stations.

=== Desktop Publishing System ===

Professional DTP configuration:
* '''A5000 4 MB/120 MB''' system
* '''SCSI podule''' for external storage
* '''Scanner interface''' for image acquisition
* '''PostScript printer''' connection
* '''Impression Publisher''' software
* '''Font collections''' on hard drive

The combination provided capabilities competitive with Macintosh systems at lower cost.

=== Software Development Platform ===

Developer configuration:
* '''A5000 4 MB/80 MB''' base
* '''8 MB RAM upgrade''' essential
* '''SCSI podule''' for backup
* '''Serial podule''' for debugging
* '''Ethernet card''' for networking
* '''Development tools''' suite

The ARM3 performance made the A5000 viable for serious software development, particularly for RISC OS and embedded ARM applications.

== Known Issues ==

Several characteristic problems affected A5000 systems:

=== Power Supply Issues ===

The internal switch-mode PSU exhibited common failures:
* '''Capacitor degradation:''' Primary and secondary capacitors fail
* '''Regulation drift:''' Voltage variations under load
* '''Thermal stress:''' Inadequate cooling in some cases
* '''Startup problems:''' Difficulty starting when cold

Regular capacitor replacement became essential for long-term reliability.

=== IDE Interface Limitations ===

The 82C711 controller imposed restrictions:
* '''Drive size limit:''' 512 MB maximum per partition
* '''No DMA:''' Processor-intensive transfers
* '''Compatibility:''' Some modern drives incompatible
* '''Performance:''' Limited to PIO Mode 2

These limitations became problematic as drive capacities increased, though third-party solutions eventually addressed some issues.

=== Battery Failures ===

The Dallas DS1287 real-time clock module contained an integrated battery:
* '''Lifetime:''' 7-10 years typical
* '''Failure mode:''' Complete module replacement required
* '''Symptoms:''' Date/time loss, configuration reset
* '''Solution:''' Module modification or replacement

The integrated battery design made replacement challenging compared to earlier removable batteries.

== Upgrade Options ==

Common upgrades extended system capabilities:

=== Memory Expansion ===

Upgrading from 2 MB to 4 MB:
1. Purchase two 1 MB 30-pin SIMMs (70ns or faster)
2. Install in empty slots 3 and 4
3. System automatically detects new memory
4. Cost in 1992: approximately £60

Upgrading to 8 MB required replacing all SIMMs with 2 MB modules, costing approximately £200 in 1993.

=== Processor Enhancements ===

Limited processor upgrades existed:
* '''ARM3 clock boost:''' 30-33 MHz possible with cooling
* '''FPA11 coprocessor:''' Floating-point acceleration
* '''Cache upgrade:''' Third-party 8 KB cache boards

The clock boost provided 20-30% performance improvement but risked system stability.

=== Storage Upgrades ===

Storage expansion options:
* '''Larger IDE drives:''' Up to 512 MB with RISC OS 3
* '''SCSI podule:''' External drive support
* '''Network storage:''' NFS via Ethernet
* '''Removable media:''' Parallel ZIP drives

Modern solutions include IDE-to-SD adapters, eliminating mechanical drive failures.

== Comparison with Competitors ==

The A5000 competed in a challenging market:

{| class="wikitable styled-table" style="width:90%; text-align:center;"
! System !! Processor !! Performance !! Price (1991) !! Market Position
|-
| A5000 2MB || ARM3 25MHz || 20,000 Dhry || £1,499 || Education/professional
|-
| 486DX-33 || Intel 486 || 16,000 Dhry || £1,800 || Business standard
|-
| Mac IIsi || 68030 20MHz || 11,000 Dhry || £2,100 || Creative professional
|-
| Amiga 3000 || 68030 25MHz || 12,500 Dhry || £2,000 || Multimedia
|}

The A5000 offered superior price-performance but suffered from limited software availability compared to PC and Macintosh platforms.

== Reliability Analysis ==

Long-term reliability studies revealed:

=== Component Failure Rates ===

{| class="wikitable styled-table" style="width:85%; text-align:center;"
! Component !! MTBF !! Failure Rate (30 years) !! Primary Cause
|-
| ARM3 processor || >100,000 hrs || <5% || Cache RAM
|-
| IDE drive || 50,000 hrs || 95% || Mechanical wear
|-
| PSU capacitors || 15,000 hrs || 100% || Electrolyte drying
|-
| DS1287 RTC || 10 years || 100% || Battery depletion
|-
| VIDC || >100,000 hrs || <2% || Very reliable
|}

Preventive maintenance significantly extended operational life, with properly maintained systems still functional after 30 years.

== Educational Impact ==

The A5000 played a crucial role in UK computing education:

=== Curriculum Support ===

The system supported diverse educational activities:
* '''Programming:''' BBC BASIC and ARM assembly
* '''Graphics:''' Vector and bitmap creation
* '''Music:''' Composition and MIDI sequencing
* '''Science:''' Data logging and analysis
* '''Technology:''' CAD and electronics design

The integrated development environment encouraged programming education, with many UK programmers learning on A5000 systems.

=== Tesco Computers for Schools ===

The A5000 featured prominently in Tesco's voucher scheme:
* '''Program duration:''' 1992-1994
* '''Voucher collection:''' Shoppers collected vouchers
* '''School redemption:''' Vouchers exchanged for computers
* '''Impact:''' Thousands of A5000s entered schools

This program significantly increased Acorn's educational market penetration, establishing RISC OS in schools previously using BBC Micros.

== Service and Support ==

Acorn provided comprehensive A5000 support:

=== Documentation ===

Available documentation included:
* '''User Guide:''' Comprehensive operating instructions
* '''Programmer's Reference:''' Complete API documentation
* '''Technical Reference:''' Hardware specifications
* '''Service Manual:''' Diagnostic and repair procedures

Documentation quality remained high, enabling third-party development and simplified maintenance.

=== Diagnostic Software ===

Diagnostic tools included:
* '''!SysMerge:''' System module updates
* '''!HForm:''' Hard drive formatting
* '''!Verify:''' Disk and memory testing
* '''!Configure:''' System settings

Third-party utilities like ZIDEFS and Killer provided additional diagnostic capabilities.

== General Maintenance ==
{{Main|Acorn Archimedes A5000 General Maintenance}}

Essential maintenance focuses on power supply capacitor inspection and replacement after 30 years of aging. The DS1287 real-time clock module requires modification or replacement when its integrated battery fails. IDE drive mechanisms need replacement with modern solid-state solutions. Cooling paths require regular cleaning to prevent thermal stress. The ARM3 processor benefits from heatsink compound replacement. Expansion slot contacts need periodic cleaning to maintain reliable podule operation.

== Troubleshooting ==
{{Main|Acorn Archimedes A5000 Troubleshooting}}

Common problems include power supply failures manifesting as inability to start or random resets, typically resolved through capacitor replacement. IDE interface errors present as drive not found or data corruption, often caused by cable problems or drive compatibility. Memory errors produce application crashes or system instability, diagnosed through systematic RAM testing. The diagnostic sequence should verify PSU voltages, test memory operation, check drive detection, and validate expansion cards.

== Capacitor Replacement Guide ==
{{Main|Acorn Archimedes A5000 Capacitor Replacement Guide}}

Critical capacitors requiring replacement include PSU primary section (47µF 400V, 100µF 200V), secondary filtering (1000µF 16V ×2, 2200µF 10V ×2, 470µF 25V ×2), and motherboard distribution (100µF 16V ×6, 47µF 16V ×8, 22µF 25V ×4). The switch-mode design requires careful attention to capacitor specifications, particularly ESR ratings. Safety precautions are essential when working with primary-side components.

== End of Production ==

Acorn discontinued the A5000 in December 1993, replacing it with the revolutionary Risc PC. Factors contributing to discontinuation included:
* Risc PC development completion
* Market demand for higher performance
* Competition from Pentium-based PCs
* Strategic platform consolidation

Remaining inventory sold through 1994, with educational discounts clearing stock. The Risc PC's modular architecture and superior performance made the A5000 obsolete, though many systems remained in service for years.

== Legacy ==

The A5000 represented the culmination of the traditional Archimedes architecture, combining ARM3 performance with cost-effective design. Its commercial success in education markets validated Acorn's strategy, though broader market penetration remained elusive. The system demonstrated that British companies could produce competitive computers, influencing subsequent ARM development.

Many technological careers began with A5000 experience, particularly in UK schools where the systems remained common through the late 1990s. The combination of accessible programming tools, reliable hardware, and comprehensive documentation created an ideal learning environment.

Modern retrocomputing enthusiasts appreciate the A5000's balance of performance, expandability, and reliability. Unlike earlier models with proprietary components, the A5000's standard memory and IDE interface simplify restoration. The relative abundance compared to other Archimedes models makes the A5000 an accessible entry point for collecting Acorn computers.

== See Also ==
* [[Acorn Archimedes A540]]
* [[Acorn Archimedes A3000]]
* [[Acorn Archimedes A3010]]
* [[Acorn Archimedes A3020]]

[[Category:Acorn Computers]]
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