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{{Infobox computer
{{Infobox computer
| name        = Acorn Archimedes A310
| name        = Acorn Archimedes A310
| image        = [[File:Acorn_Archimedes_A310.jpg|250px]]
| image        = [[File:Acorn_Archimedes_A305.jpg|250px]]
| caption      = Acorn Archimedes A310
| caption      = Archimedes 300-series system unit. The A305 and A310 are physically identical; only the DRAM fitment differs.
| manufacturer = Acorn Computers Ltd
| manufacturer = Acorn Computers Ltd
| type        = Personal Computer
| type        = Personal computer (three-box desktop)
| release date = June 1987
| release date = June 1987
| discontinued = 1989
| discontinued = 1989
| price        = £875 (1987)
| price        = £875 ex VAT (base), £1,075 ex VAT with colour monitor
| cpu          = ARM2 @ 8 MHz
| cpu          = ARM2 @ 8 MHz (24 MHz master oscillator)
| memory      = 1 MB RAM (expandable to 4 MB)
| memory      = 1 MB RAM (32 × 4464 DRAM); larger third-party upgrades available
| storage      = 3.5" floppy drive (800 KB), optional hard drive
| storage      = 3.5" floppy drive, 1 MB unformatted (800 KB ADFS E)
| display      = 640×512 (16 colours), 640×256 (256 colours), 1152×896 (monochrome)
| display      = Analogue RGB, mono composite; 640×256 in 256 colours, 640×512 in 16 colours on a multisync
| sound        = 8-channel stereo, 8-bit logarithmic DAC
| sound        = 8-channel, 8-bit logarithmic (VIDC1a)
| dimensions  = 415 mm × 355 mm × 104 mm
| dimensions  = 362 mm wide × 406 mm deep × 97 mm high (main unit, excluding feet)
| weight      = 8 kg
| os          = Arthur 0.30, then Arthur 1.20; upgradeable to RISC OS 2 and, with a carrier board, RISC OS 3
| os          = Arthur 0.30 (later RISC OS 2.00)
| predecessor  = BBC Master series (no page yet)
| predecessor  = [[BBC Master]]
| successor    = [[Acorn Archimedes A3000]]
| successor    = [[Acorn Archimedes A410]], [[Acorn Archimedes A3000]]
| model        = AKB15
| codename    = Fairway
| model        = A305, A310, A440
}}
}}
<templatestyles src="Template:StyledTable/styles.css" />
The '''Acorn Archimedes A310''' was launched in June 1987 alongside the [[Acorn Archimedes A305|A305]]. The two machines share the 276,000 motherboard and differ only in the amount of DRAM fitted: 1 MB in the A310, 0.5 MB in the A305. They were the first RISC-processor computers sold to the general public.<ref name="chris300">Whytehead, Chris. [https://chrisacorns.computinghistory.org.uk/Computers/A300.html "Acorn Archimedes A300 Series"], Chris's Acorns / The Centre for Computing History. Machine-by-machine specification tables, part numbers and measured benchmark figures.</ref>


The '''Acorn Archimedes A310''' was the first mass-market computer to use a RISC processor, released in June 1987 alongside the A305 and A440 models. Built around Acorn's revolutionary ARM2 processor, the A310 delivered unprecedented performance for its price point, outperforming the Motorola 68000-based competition while maintaining full BBC BASIC compatibility through its advanced operating system.
This page covers the parts specific to the A310. The chip set, screen modes, expansion, backup batteries, power rails, Acorn field changes and capacitor values are shared with the A305 and are documented on the [[Acorn Archimedes A305]] page.


== Architecture ==
== Prices ==


The A310's architecture represented a radical departure from conventional microcomputer design. At its core, the ARM2 processor implemented a Reduced Instruction Set Computer philosophy with a streamlined 32-bit architecture. The processor executed most instructions in a single cycle, achieving 4-8 MIPS performance at 8 MHz when contemporary 68000 and 80286 processors struggled to reach 2 MIPS at similar clock speeds.
From Acorn's 1987 retail price list, ex VAT:<ref name="price87">Acorn Computers Limited, ''High Performance Computer Systems Retail Price List'' and ''Pricing'' sheet, 1987. Hosted on this wiki: [[Acorn Archimedes Retail Price List 1987]].</ref>


=== System Components ===
{| class="wikitable styled-table" style="width:75%; text-align:center;"
 
! Product code !! Configuration !! RRP ex VAT !! RRP inc VAT
{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Component !! Part Number !! Function !! Key Features
|-
|-
| '''ARM2''' || VL2333-PC10 || 32-bit RISC CPU || 25,000 transistors, 68-pin PLCC, <1W power
| AKB15 || A310, no monitor || £875.00 || £1,004.00
|-
|-
| '''MEMC''' || VL7991-PC11 || Memory controller || CAM-based MMU, DMA control, 84-pin PLCC
| AKB15/AKF01 || A310 with mono monitor || £925.00 || £1,061.50
|-
|-
| '''VIDC''' || VL475-PC12 || Video/sound controller || 4096 colors, 8-channel DMA sound, 88-pin PLCC
| AKB15/AKF11 || A310 with colour monitor || £1,075.00 || £1,234.00
|-
| '''IOC''' || VL2966-PC10 || I/O controller || Timers, interrupts, peripherals, 68-pin PLCC
|}
|}


The system employed four custom VLSI chips that Acorn designed specifically for the Archimedes range. These chips communicated via a high-speed local bus operating at 8 MHz, with MEMC coordinating all memory access to prevent conflicts between the processor, video, and sound subsystems.
The figure of £999 that circulates for the A310 is the price of an '''A305''' with a colour monitor, not an A310 of any kind.<ref name="price87" />


=== Memory Map ===
A variant, the '''A310M''' Archimedes Music Workstation, was sold under product code AKB30.<ref name="chris300" /><ref name="chrisarc">Whytehead, Chris. [https://chrisacorns.computinghistory.org.uk/Computers/Archimedes.html "Archimedes"], Chris's Acorns / The Centre for Computing History. Acorn product-code list for the Archimedes range.</ref>


{| class="wikitable styled-table" style="width:70%; text-align:center;"
== Processor and memory ==
|+'''A310 Memory Organization'''
! Address Range !! Size !! Function !! Access Speed
|-
| $0000000 – $01FFFFF || 32 MB || Logical RAM space || 2-4 cycles
|-
| $0200000 – $02FFFFF || 1 MB || Physical RAM || Fast page mode
|-
| $1F00000 – $1FFFFFF || 1 MB || I/O space || 8 MHz
|-
| $2000000 – $2FFFFFF || 16 MB || Physical space || DMA/Video
|-
| $3000000 – $33FFFFF || 4 MB || ROM space || 2 cycles
|-
| $3400000 – $3FFFFFF || 12 MB || Expansion ROM || Variable
|}


MEMC implemented an unusual but efficient memory management scheme using a CAM (Content Addressable Memory) array providing hardware page translation without the complexity of a full MMU. This design supported 32 logical pages of 32 KB each, allowing sophisticated memory protection while maintaining single-cycle access for sequential addresses.
The ARM2 is a 32-bit processor with 26-bit addressing, clocked at 4 or 8 MHz from a single 24 MHz master oscillator depending on the memory cycle. Acorn quoted system performance as "typically 4 MIPS".<ref name="sm300">Acorn Computers Limited, ''Archimedes 300 Series Module Level Service Manual'', part number 0476,140, Issue 1, April 1988. Section 1.2 Technical Specification, section 5 Connectors, interfaces, links and test points, and appendices 7.1 and 7.2. Hosted on this wiki: [[Archimedes 300 Series Service Manual]].</ref>


== Hardware Design ==
The A310 has the full complement of thirty-two 4464 DRAMs — 64K × 4 bits at 120 ns — giving 1 MB. This is the maximum the board takes as Acorn shipped it.<ref name="sm300" /> Several third parties sold 2 MB and 4 MB upgrades; the smaller ones augmented the on-board memory and the larger ones replaced it entirely. Chris Whytehead's restored A310s carry IFEL 4 MB boards, one with the original MEMC1 and the others with MEMC1a.<ref name="chris300" />


The A310 motherboard measured 355mm × 245mm and employed a four-layer PCB design to minimize signal interference. The layout positioned the four custom chips in a square formation to minimize trace lengths, with the ARM2 and MEMC chips requiring precise timing relationships.
ROM is 512 KB as standard in four 32-pin sockets.<ref name="sm300" />


=== ARM2 Processor Details ===
== Operating system ==


The ARM2 processor contained approximately 25,000 transistors fabricated on a 3µm CMOS process. Despite its 32-bit architecture, the chip used only 68 pins and consumed less than 1 watt of power. The processor implemented 27 32-bit registers arranged in multiple banks for rapid context switching during interrupts.
A310s shipped first with Arthur 0.30 and, from September 1987, Arthur 1.20. Acorn's own Arthur ROM fitting instructions make clear that Arthur 1.10 and Arthur 1.20 are the same release.<ref name="chris300" />


{| class="wikitable styled-table" style="width:85%; text-align:center;"
Arthur 1.20's desktop was written in BASIC and was very limited — a palette selector, calculator, notepad, clock, calendar and diary, with an icon bar that could format discs.<ref name="chris300" /> RISC OS 2.00, dated 5 October 1988, replaced it and introduced the cooperative multitasking desktop proper. RISC OS 2 is a straight ROM swap on this board. RISC OS 3.10 and later need a ROM carrier board — IFEL's is the one usually found — because the RISC OS 3 ROM set does not fit the board's native four sockets.<ref name="chris300" />
! Feature !! Specification !! Implementation
|-
| '''Pipeline''' || 3-stage || Fetch, decode, execute
|-
| '''Registers''' || 27× 32-bit || 16 visible, banked for modes
|-
| '''Addressing''' || 26-bit || 64 MB address space
|-
| '''Instructions''' || Fixed 32-bit || Conditional execution on all
|-
| '''Barrel shifter''' || 32-bit || Single-cycle shifts/rotates
|-
| '''Multiply''' || 32×32→32 || 2-16 cycles depending on data
|}


The three-stage pipeline allowed the ARM2 to fetch, decode, and execute instructions simultaneously. Conditional execution on all instructions eliminated many branch operations, improving pipeline efficiency. The barrel shifter permitted complex address calculations and bit manipulation in a single cycle, compensating for the limited instruction set.
== Expansion ==


== Video System ==
The A310 ships with no expansion slots. The Acorn AKA01 backplane (part 0176,040) adds '''two''' podule positions; third-party four-slot backplanes for the 305/310, such as IFEL's, came later.<ref name="chris300" /><ref name="sm300" /> Total draw from the backplane must not exceed 20 W, and coprocessor podules are not supported on this board.<ref name="sm300" />


VIDC provided exceptional graphics capabilities for 1987, supporting multiple resolutions and color depths through programmable video timing. The chip contained sophisticated palette handling and hardware cursor support, with all video data fetched via DMA without processor intervention.
The area on the middle right of the motherboard is where the hard disc controller would sit — it is '''not''' fitted on any 300-series machine, unlike the [[Acorn Archimedes A440|A440]]. A hard disc on an A310 means the AKD52 podule-based upgrade or a third-party SCSI or IDE podule.<ref name="chris300" /><ref name="sm300" />


=== Display Modes ===
== Decoupling capacitors C37, C38 and C39 ==


{| class="wikitable styled-table" style="width:90%; text-align:center;"
Acorn specified three 100 µF 16 V 20% tantalum capacitors, part 0611,101, at C37, C38 and C39 as supply decoupling on the main PCB.<ref name="cl300">Acorn Computers Limited, ''Archimedes 300 Series Service Manual Component Level Supplement'', part number 0476,145, Issue 1, October 1988. Section 5.1 Parts Lists. Hosted on this wiki: [[Archimedes 300 Series Service Manual Component Level Supplement]].</ref> C37 decouples the 12 V line, so a 16 V part sits at only 1.33 times the rail it is decoupling. Tantalums are intolerant of over-voltage and fail short, and these positions are the ones most often found burnt on surviving 300-series boards, typically presenting as a machine that will not start.
! Mode !! Resolution !! Colors !! Refresh !! Memory !! Bandwidth
|-
| 0 || 640×256 || 2 || 50 Hz || 20 KB || 1 MB/s
|-
| 9 || 640×256 || 16 || 50 Hz || 80 KB || 4 MB/s
|-
| 10 || 640×256 || 256 || 50 Hz || 160 KB || 8 MB/s
|-
| 12 || 640×512 || 16 || 50 Hz || 160 KB || 8 MB/s
|-
| 13 || 640×512 || 256 || 50 Hz || 320 KB || 16 MB/s
|-
| 15 || 640×512 || 16 || 50 Hz || 160 KB || 8 MB/s
|-
| 20 || 640×512 || 16 || 70 Hz || 160 KB || 11.2 MB/s
|-
| 21 || 640×512 || 256 || 70 Hz || 320 KB || 22.4 MB/s
|-
| 23 || 1152×896 || 2 || 75 Hz || 128 KB || 9.6 MB/s
|}


Video timing was fully programmable, allowing custom display modes beyond the standard configurations. The chip generated separate horizontal and vertical sync signals compatible with both standard and multisync monitors. Border color and display blanking were software-controlled, enabling overscan effects and smooth mode switching.
If you replace them, a higher-voltage part is a sensible substitution in the C37 position. Check the PSU rails at PL5 (+12 V), PL6 (0 V), PL7 (+5 V) and PL8 (−5 V) before and after.<ref name="sm300" />


== Sound System ==
The full capacitor list for this board is on the [[Acorn Archimedes A305#Capacitors|A305 page]], from Acorn's component-level parts list.<ref name="cl300" />


The VIDC sound system represented a significant advancement over previous 8-bit computers. Eight independent DMA channels could each play different samples at varying rates and stereo positions.
== Measured performance ==


=== Audio Specifications ===
Chris Whytehead's documented A310s give the only published measurements taken on a known configuration of this board:<ref name="chris300" />


{| class="wikitable styled-table" style="width:85%; text-align:center;"
{| class="wikitable styled-table" style="width:85%; text-align:center;"
! Parameter !! Specification !! Notes
! Machine !! CPU !! Memory controller !! OS !! ARMSi v4.0 MIPS !! SICK Dhrystone/s !! kWhetstone/s
|-
| '''Channels''' || 8 independent || DMA-driven
|-
| '''Sample format''' || 8-bit µ-law || ~12-bit linear equivalent
|-
| '''Sample rates''' || 3.125 - 48 kHz || Per channel
|-
| '''Stereo positions''' || 7 per channel || Hardware panning
|-
|-
| '''Buffer size''' || 4 words/channel || Interrupt on empty
| A310 (2) || ARM2 8 MHz || MEMC1a || RISC OS 2.00 || 4.80 || 4,797 || —
|-
|-
| '''Output''' || Stereo 3.5mm jack || Line level
| A310 (3) || CJE Micros ARM3 25 MHz || MEMC1a || RISC OS 3.10 || 12.75 || 17,326 || 213
|}
|}


Each channel supported seven stereo positions (left, center-left, center, center-right, right, and two intermediate positions), enabling sophisticated spatial effects. The logarithmic DAC encoding provided better perceived quality than linear 8-bit systems, approximating 12-bit linear resolution for typical audio material.
Acorn's own marketing figure was 4 MIPS.<ref name="sm300" /> Higher figures quoted for the Archimedes at launch — 4.5 MIPS, and in some contemporary reports 18 MIPS — are peak or synthetic numbers and are not supported by any measurement on a documented machine.
 
== Input/Output Systems ==
 
The A310 provided comprehensive I/O capabilities through multiple interfaces. The IOC chip managed most standard peripherals while the motherboard included dedicated controllers for floppy drives and optional hard drives.
 
=== Port Specifications ===
 
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Interface !! Controller !! Connector !! Speed !! Protocol
|-
| '''Serial''' || 6551 ACIA || 9-pin D-sub || 19200 bps || RS423
|-
| '''Parallel''' || 8-bit latch || 25-pin D-sub || 50 KB/s || Centronics
|-
| '''Floppy''' || WD1772 || 34-pin IDC || 31.25 KB/s || ADFS format
|-
| '''SCSI''' || Optional NCR5380 || 50-pin IDC || 1 MB/s || SCSI-1
|-
| '''Econet''' || 68B54 ADLC || 5-pin DIN || 200 kbps || Network
|-
| '''Mouse''' || Quadrature || 9-pin mini-DIN || 100 Hz || X/Y encoders
|-
| '''Keyboard''' || 8051 MCU || 6-pin mini-DIN || Serial || Custom protocol
|}
 
The WD1772 floppy disk controller operated at 8 MHz, supporting both 250 kbps (double density) and 500 kbps (high density) data rates. The controller interfaced directly with the IOC chip for DMA transfers. The ADFS (Advanced Disc Filing System) implemented a proprietary format storing 800 KB on double-density disks through efficient sector allocation.
 
=== Expansion Bus ===
 
Four 96-pin DIN 41612 expansion slots provided access to the full processor bus. These "podule" slots supported sophisticated expansion capabilities:
 
* '''Bus width:''' 8-bit or 16-bit data transfers
* '''Addressing:''' 24-bit address space per slot
* '''Speed:''' 2 MHz (slow) or 8 MHz (fast) operation
* '''Power:''' +5V @ 200mA, ±12V @ 100mA per slot
* '''Interrupts:''' IRQ and FIQ support
* '''DMA:''' Direct memory access capability
 
Common expansion cards included SCSI interfaces, Ethernet adapters, video digitizers, MIDI interfaces, and ROM/RAM expansion boards. The podule specification allowed automatic configuration, with each card identifying itself to the operating system at startup.
 
== Operating System Evolution ==
 
The A310 initially shipped with Arthur 0.30, a rudimentary operating system providing basic functionality while RISC OS was under development. Arthur included a simple command-line interface, BBC BASIC V interpreter, and essential filing system support.
 
=== Operating System Comparison ===
 
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Feature !! Arthur 0.30/1.20 !! RISC OS 2.00
|-
| '''Desktop''' || Single-tasking || Cooperative multitasking
|-
| '''Memory management''' || Static allocation || Dynamic areas
|-
| '''Font system''' || Bitmap only || Outline fonts
|-
| '''File systems''' || ADFS, DFS || ADFS, DFS, NetFS, RamFS
|-
| '''Applications''' || Command-line tools || Paint, Draw, Edit included
|-
| '''Window manager''' || Basic windowing || Full WIMP environment
|-
| '''ROM size''' || 512 KB || 2 MB
|}
 
RISC OS 2.00, released in April 1989, transformed the A310 into a sophisticated GUI-based system. The operating system resided in ROM, providing instant startup and immunity from disk corruption. The modular architecture allowed individual components to be updated or replaced without affecting system stability.
 
== Memory and Performance ==
 
The A310 shipped with 1 MB of RAM as standard, organized as four 256K×9-bit SIMMs providing byte-wide error detection. Memory bandwidth limitations significantly affected system performance in high-resolution modes.
 
=== Performance Impact by Display Mode ===
 
{| class="wikitable styled-table" style="width:85%; text-align:center;"
! Mode !! Resolution !! DMA Overhead !! CPU Performance
|-
| 0 || 640×256×2 || 6% || 94% of maximum
|-
| 12 || 640×512×16 || 25% || 75% of maximum
|-
| 13 || 640×512×256 || 50% || 50% of maximum
|-
| 21 || 640×512×256 @ 70Hz || 70% || 30% of maximum
|}
 
Memory expansion to 4 MB required replacing the standard modules with 1M×9-bit SIMMs. The system reserved the top 32 KB of physical memory for screen display, with additional allocations for sound buffers and system workspace. Contemporary benchmarks demonstrated the A310's superiority, with Dhrystone yields of 4100 iterations per second compared to 1800 for a 16 MHz 80286.
 
== Power Supply ==
 
The A310 employed a linear power supply rated at 45 watts continuous output. The transformer-based design provided excellent regulation but generated substantial heat.
 
=== Power Specifications ===
 
{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Rail !! Voltage !! Current !! Usage
|-
| Primary || +5V || 6A || Logic circuits
|-
| Drive || +12V || 1.5A || Floppy/hard drives
|-
| Serial || -5V || 100mA || RS423 levels
|-
| Auxiliary || -12V || 50mA || Optional peripherals
|}
 
The conservative design contributed to long-term reliability, though electrolytic capacitors eventually degrade, causing ripple and regulation problems that manifest as system instability or startup failures.
 
== Manufacturing Variants ==
 
Acorn produced several PCB revisions addressing design issues and reducing costs:
 
{| class="wikitable styled-table" style="width:85%; text-align:center;"
! Issue !! Production Period !! Changes !! Known Problems
|-
| 1 || Jun-Dec 1987 || Original design || Timing marginal, Arthur bugs
|-
| 2 || Jan-Sep 1988 || PAL integration || Podule compatibility
|-
| 3 || Oct 1988-1989 || RISC OS ready || Battery placement
|-
| 4 || 1989 || Cost reduced || Some incompatibilities
|}
 
Component substitutions occurred throughout production. Early machines used Motorola 68B51 serial chips, later replaced with Rockwell 65C51 variants. RAM manufacturers varied between Samsung, NEC, and Hitachi, with minor timing differences affecting marginal systems.
 
== Known Issues ==


Several design decisions affected long-term reliability:
== The MEMC1a ==


* '''Battery leakage:''' 3.6V NiCd CMOS battery corrodes PCB traces after 10-15 years
Later 300-series machines and all A400/1 machines use the MEMC1a in place of the original MEMC1. Acorn described the change as giving "a slight performance improvement".<ref name="chris4001">Whytehead, Chris. [https://chrisacorns.computinghistory.org.uk/Computers/A4001.html "Acorn Archimedes A400/1 Series"], Chris's Acorns / The Centre for Computing History.</ref> The frequently repeated claim of a 10% gain is not supported by the measured figures: an ARM2 A310 with MEMC1a returns 4.80 MIPS on ARMSi and a MEMC1a [[Acorn Archimedes A3000|A3000]] 4.82, against 4.56 for a MEMC1 [[Acorn Archimedes A440|A440]].<ref name="chris300" /><ref name="chris3000">Whytehead, Chris. [https://chrisacorns.computinghistory.org.uk/Computers/A3000.html "BBC A3000"], Chris's Acorns / The Centre for Computing History.</ref><ref name="chris400">Whytehead, Chris. [https://chrisacorns.computinghistory.org.uk/Computers/A400.html "Acorn Archimedes A400 Series"], Chris's Acorns / The Centre for Computing History.</ref> The MEMC1a's real significance is that it will run at a 12 MHz memory clock, which is what the [[Acorn Archimedes A540|A540]] and [[Acorn Archimedes A5000|A5000]] use; on the A310 the memory clock stays at 8 MHz.<ref name="chris540">Whytehead, Chris. [https://chrisacorns.computinghistory.org.uk/Computers/A540.html "Acorn Archimedes A540"], Chris's Acorns / The Centre for Computing History.</ref><ref name="chris5000">Whytehead, Chris. [https://chrisacorns.computinghistory.org.uk/Computers/A5000.html "Acorn A5000"], Chris's Acorns / The Centre for Computing History.</ref>
* '''Thermal stress:''' Linear PSU operates near limits, stressing capacitors
* '''Keyboard controller:''' 8051 firmware corruption requires chip replacement
* '''ROM bugs:''' Arthur versions exhibit memory corruption and crashes
* '''Podule timing:''' Some expansion cards require Issue 2+ motherboards


Early ROM versions contained numerous bugs. Arthur 0.30 and 1.20 exhibited memory corruption under specific circumstances, random crashes during disk access, and compatibility problems with certain podule cards. RISC OS 2.00 resolved most issues but introduced new problems with some existing software.
Where the MEMC1a matters on this board is that it is required for the larger third-party memory upgrades.<ref name="chris300" />


== General Maintenance ==
== Maintenance and repair ==
{{Main|Acorn Archimedes A310 General Maintenance}}


Regular maintenance extends operational lifetime significantly. Critical tasks include CMOS battery replacement before leakage occurs, power supply capacitor inspection for bulging or leakage, and ventilation path cleaning to prevent thermal stress. The keyboard requires periodic cleaning to maintain reliable operation, while the floppy drive needs lubrication and alignment checks every 2-3 years.
* '''Remove the two AA alkaline cells''' from the holder riveted to the base metalwork. Acorn specified annual replacement; cells left in for decades leak and attack the board. See [[Battery Explosion, Capacitor or Corrosion Damage]].
* '''Check C37, C38 and C39''' — see above.
* '''Check the PSU rails''' at PL5–PL8. A clicking PSU means a short between outputs or a failed supply.<ref name="sm300" />
* '''Check the ROM type links''' LK2, LK6 and LK12 after any ROM change.<ref name="sm300" />
* '''Floppy drive''' — see [[Floppy Drive Repair]].
* '''Tools''' — see [[Recommended Tools]].


== Troubleshooting ==
Acorn's documented production faults and field change orders for this board — the speaker noise modification, the RGB level change, the video noise diode, the Q9/Q11 audio transistor issue and the Issue 1 serial port links — are listed on the [[Acorn Archimedes A305#Acorn production and field changes|A305 page]].<ref name="sm300" />
{{Main|Acorn Archimedes A310 Troubleshooting}}


Common failures follow predictable patterns. Power supply problems manifest as startup failures or random resets, usually traced to degraded capacitors in the main filter section. Video corruption indicates VIDC timing issues or RAM failures, diagnosed through systematic memory testing. Floppy drive errors result from alignment drift or WD1772 controller chip failure, requiring careful adjustment or component replacement.
Component-level fault-finding is in the [[Archimedes 300 Series Service Manual Component Level Supplement]]; module-level procedures are in the [[Archimedes 300 Series Service Manual]].


== Capacitor Replacement Guide ==
== See also ==
{{Main|Acorn Archimedes A310 Capacitor Replacement Guide}}


After 35+ years, electrolytic capacitors require replacement. Critical components include:
* [[Acorn Archimedes A305]] — the same board with half the memory
* '''PSU main filter:''' 4700µF 25V
* [[Acorn Archimedes A440]] — 4 MB flagship of the same 1987 range
* '''PSU auxiliary:''' 1000µF 16V (×3), 470µF 25V (×2)
* [[Acorn Archimedes A3000]] — the 1989 replacement for the 300 series
* '''Motherboard:''' 100µF 16V (×6), 47µF 16V (×8), 10µF 25V (×4)
* [[Archimedes 300 Series Service Manual]]
* '''High-voltage:''' 100µF 200V (×2) in PSU primary


== Technical Legacy ==
== References ==


The A310 established ARM processors in the personal computer market, demonstrating RISC architecture advantages over complex instruction set competitors. While commercial success remained limited outside education markets, the technical innovations influenced subsequent computer designs. ARM processors, refined through successive generations, now dominate mobile computing, validating Acorn's architectural decisions from 1987.
<references />


== See Also ==
{{Navbox-AcornComputers|state=collapsed}}
* [[Acorn Archimedes A305]]
* [[Acorn Archimedes A410]]
* [[Acorn Archimedes A440]]
* [[Acorn Archimedes A3000]]
* [[BBC Master]]


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

Latest revision as of 02:56, 23 September 2026

Acorn Archimedes A310
Archimedes 300-series system unit. The A305 and A310 are physically identical; only the DRAM fitment differs.
Specifications
ManufacturerAcorn Computers Ltd
TypePersonal computer (three-box desktop)
ReleasedJune 1987
Discontinued1989
Intro price£875 ex VAT (base), £1,075 ex VAT with colour monitor
CPUARM2 @ 8 MHz (24 MHz master oscillator)
Memory1 MB RAM (32 × 4464 DRAM); larger third-party upgrades available
Storage3.5" floppy drive, 1 MB unformatted (800 KB ADFS E)
DisplayAnalogue RGB, mono composite; 640×256 in 256 colours, 640×512 in 16 colours on a multisync
Sound8-channel, 8-bit logarithmic (VIDC1a)
Dimensions362 mm wide × 406 mm deep × 97 mm high (main unit, excluding feet)
OS / FirmwareArthur 0.30, then Arthur 1.20; upgradeable to RISC OS 2 and, with a carrier board, RISC OS 3
PredecessorBBC Master series (no page yet)
SuccessorAcorn Archimedes A3000
Model no.AKB15

The Acorn Archimedes A310 was launched in June 1987 alongside the A305. The two machines share the 276,000 motherboard and differ only in the amount of DRAM fitted: 1 MB in the A310, 0.5 MB in the A305. They were the first RISC-processor computers sold to the general public.[1]

This page covers the parts specific to the A310. The chip set, screen modes, expansion, backup batteries, power rails, Acorn field changes and capacitor values are shared with the A305 and are documented on the Acorn Archimedes A305 page.

Prices

[edit | edit source]

From Acorn's 1987 retail price list, ex VAT:[2]

Product code Configuration RRP ex VAT RRP inc VAT
AKB15 A310, no monitor £875.00 £1,004.00
AKB15/AKF01 A310 with mono monitor £925.00 £1,061.50
AKB15/AKF11 A310 with colour monitor £1,075.00 £1,234.00

The figure of £999 that circulates for the A310 is the price of an A305 with a colour monitor, not an A310 of any kind.[2]

A variant, the A310M Archimedes Music Workstation, was sold under product code AKB30.[1][3]

Processor and memory

[edit | edit source]

The ARM2 is a 32-bit processor with 26-bit addressing, clocked at 4 or 8 MHz from a single 24 MHz master oscillator depending on the memory cycle. Acorn quoted system performance as "typically 4 MIPS".[4]

The A310 has the full complement of thirty-two 4464 DRAMs — 64K × 4 bits at 120 ns — giving 1 MB. This is the maximum the board takes as Acorn shipped it.[4] Several third parties sold 2 MB and 4 MB upgrades; the smaller ones augmented the on-board memory and the larger ones replaced it entirely. Chris Whytehead's restored A310s carry IFEL 4 MB boards, one with the original MEMC1 and the others with MEMC1a.[1]

ROM is 512 KB as standard in four 32-pin sockets.[4]

Operating system

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A310s shipped first with Arthur 0.30 and, from September 1987, Arthur 1.20. Acorn's own Arthur ROM fitting instructions make clear that Arthur 1.10 and Arthur 1.20 are the same release.[1]

Arthur 1.20's desktop was written in BASIC and was very limited — a palette selector, calculator, notepad, clock, calendar and diary, with an icon bar that could format discs.[1] RISC OS 2.00, dated 5 October 1988, replaced it and introduced the cooperative multitasking desktop proper. RISC OS 2 is a straight ROM swap on this board. RISC OS 3.10 and later need a ROM carrier board — IFEL's is the one usually found — because the RISC OS 3 ROM set does not fit the board's native four sockets.[1]

Expansion

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The A310 ships with no expansion slots. The Acorn AKA01 backplane (part 0176,040) adds two podule positions; third-party four-slot backplanes for the 305/310, such as IFEL's, came later.[1][4] Total draw from the backplane must not exceed 20 W, and coprocessor podules are not supported on this board.[4]

The area on the middle right of the motherboard is where the hard disc controller would sit — it is not fitted on any 300-series machine, unlike the A440. A hard disc on an A310 means the AKD52 podule-based upgrade or a third-party SCSI or IDE podule.[1][4]

Decoupling capacitors C37, C38 and C39

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Acorn specified three 100 µF 16 V 20% tantalum capacitors, part 0611,101, at C37, C38 and C39 as supply decoupling on the main PCB.[5] C37 decouples the 12 V line, so a 16 V part sits at only 1.33 times the rail it is decoupling. Tantalums are intolerant of over-voltage and fail short, and these positions are the ones most often found burnt on surviving 300-series boards, typically presenting as a machine that will not start.

If you replace them, a higher-voltage part is a sensible substitution in the C37 position. Check the PSU rails at PL5 (+12 V), PL6 (0 V), PL7 (+5 V) and PL8 (−5 V) before and after.[4]

The full capacitor list for this board is on the A305 page, from Acorn's component-level parts list.[5]

Measured performance

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Chris Whytehead's documented A310s give the only published measurements taken on a known configuration of this board:[1]

Machine CPU Memory controller OS ARMSi v4.0 MIPS SICK Dhrystone/s kWhetstone/s
A310 (2) ARM2 8 MHz MEMC1a RISC OS 2.00 4.80 4,797 —
A310 (3) CJE Micros ARM3 25 MHz MEMC1a RISC OS 3.10 12.75 17,326 213

Acorn's own marketing figure was 4 MIPS.[4] Higher figures quoted for the Archimedes at launch — 4.5 MIPS, and in some contemporary reports 18 MIPS — are peak or synthetic numbers and are not supported by any measurement on a documented machine.

The MEMC1a

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Later 300-series machines and all A400/1 machines use the MEMC1a in place of the original MEMC1. Acorn described the change as giving "a slight performance improvement".[6] The frequently repeated claim of a 10% gain is not supported by the measured figures: an ARM2 A310 with MEMC1a returns 4.80 MIPS on ARMSi and a MEMC1a A3000 4.82, against 4.56 for a MEMC1 A440.[1][7][8] The MEMC1a's real significance is that it will run at a 12 MHz memory clock, which is what the A540 and A5000 use; on the A310 the memory clock stays at 8 MHz.[9][10]

Where the MEMC1a matters on this board is that it is required for the larger third-party memory upgrades.[1]

Maintenance and repair

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  • Remove the two AA alkaline cells from the holder riveted to the base metalwork. Acorn specified annual replacement; cells left in for decades leak and attack the board. See Battery Explosion, Capacitor or Corrosion Damage.
  • Check C37, C38 and C39 — see above.
  • Check the PSU rails at PL5–PL8. A clicking PSU means a short between outputs or a failed supply.[4]
  • Check the ROM type links LK2, LK6 and LK12 after any ROM change.[4]
  • Floppy drive — see Floppy Drive Repair.
  • Tools — see Recommended Tools.

Acorn's documented production faults and field change orders for this board — the speaker noise modification, the RGB level change, the video noise diode, the Q9/Q11 audio transistor issue and the Issue 1 serial port links — are listed on the A305 page.[4]

Component-level fault-finding is in the Archimedes 300 Series Service Manual Component Level Supplement; module-level procedures are in the Archimedes 300 Series Service Manual.

See also

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References

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  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Whytehead, Chris. "Acorn Archimedes A300 Series", Chris's Acorns / The Centre for Computing History. Machine-by-machine specification tables, part numbers and measured benchmark figures.
  2. ↑ 2.0 2.1 Acorn Computers Limited, High Performance Computer Systems Retail Price List and Pricing sheet, 1987. Hosted on this wiki: Acorn Archimedes Retail Price List 1987.
  3. ↑ Whytehead, Chris. "Archimedes", Chris's Acorns / The Centre for Computing History. Acorn product-code list for the Archimedes range.
  4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 Acorn Computers Limited, Archimedes 300 Series Module Level Service Manual, part number 0476,140, Issue 1, April 1988. Section 1.2 Technical Specification, section 5 Connectors, interfaces, links and test points, and appendices 7.1 and 7.2. Hosted on this wiki: Archimedes 300 Series Service Manual.
  5. ↑ 5.0 5.1 Acorn Computers Limited, Archimedes 300 Series Service Manual Component Level Supplement, part number 0476,145, Issue 1, October 1988. Section 5.1 Parts Lists. Hosted on this wiki: Archimedes 300 Series Service Manual Component Level Supplement.
  6. ↑ Whytehead, Chris. "Acorn Archimedes A400/1 Series", Chris's Acorns / The Centre for Computing History.
  7. ↑ Whytehead, Chris. "BBC A3000", Chris's Acorns / The Centre for Computing History.
  8. ↑ Whytehead, Chris. "Acorn Archimedes A400 Series", Chris's Acorns / The Centre for Computing History.
  9. ↑ Whytehead, Chris. "Acorn Archimedes A540", Chris's Acorns / The Centre for Computing History.
  10. ↑ Whytehead, Chris. "Acorn A5000", Chris's Acorns / The Centre for Computing History.


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