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Acorn A3010, A3020 and A4000 Technical Reference Manual

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The Acorn A3010/A3020/A4000 Technical Reference Manual is Acorn Computers' hardware reference for the Acorn Archimedes A3010, Acorn Archimedes A3020 and Acorn Archimedes A4000, Issue 1, January 1993, copyright Acorn Computers Limited 1991, 1992, published by Acorn Computers Technical Publications Department. The hosted scan has 66 pages and no text layer.

The scan's page order follows the way the sheets were fed through a scanner: PDF pages 1-33 are the front of each sheet in order (the odd printed pages), and PDF pages 34-66 are the backs in reverse order. Printed p. 1-18, for example, is PDF p. 56.

Contents

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Acorn's contents list (p. iii), with printed page numbers:

  • About this manual, p. iv; Safety, p. iv
  • Part 1, System description, p. 1-1: ARM250 1-2, system timing 1-2, memory system 1-4, I/O system 1-4, floppy disc drive 1-8, IDE hard disc interface (not A3010) 1-11, video circuit 1-11, audio circuit 1-13, keyboard and mouse 1-13, power supply 1-18, ARM250 pin out 1-18, links 1-20, plugs 1-20, sockets 1-21
  • Part 2, Parts lists, p. 2-1: A4000 main PCB 2-1; A3010 1M final assembly 2-4; A3010 2M final assembly 2-5; A3010 1M main PCB 2-5; A3010 2M main PCB 2-9; A3010 1M (ARM250) main PCB 2-13; A3010 2M (ARM250) main PCB 2-17; A3020 2M final assembly 2-21; A3020 2M HD final assembly 2-22; A3020 2M main PCB 2-22; A3020/A4000 Econet PCB 2-26; A3020/A3010 CPU module PCB 2-27
  • Appendix A, monitor adaptor cables, p. A-1
  • Appendix B, timing diagrams, p. B-1
  • Appendix C, RAM chip signals, p. C-1
  • Appendix D, engineering drawings, p. D-1

From the A3020 lists onwards the contents page is one page early: the A3020 2M final assembly list starts on p. 2-22, the A3020 2M HD final assembly and A3020 2M main PCB lists on p. 2-23, the Econet list on p. 2-27 and the CPU module list on p. 2-28.

Each parts list gives the Acorn part number, description and quantity for every designator on that board, so the right list can be matched to the board in hand. The separate "ARM250" lists are for the later boards: Appendix D (p. D-1) explains that early production used a main PCB carrying a daughter card with a discrete version of the ARM250, clocked by 36 MHz and 24 MHz oscillators in place of the single 72 MHz oscillator, and that the battery position differs between the two boards.

What it settles

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Acorn's feature table (p. 1-1):

A3010, A3020 and A4000 compared (Technical Reference Manual, p. 1-1)
Feature A3010 A3020 A4000
Design Single box Single box Twin box
Computer system IC 12 MHz ARM250 12 MHz ARM250 12 MHz ARM250
Base memory 1 MB DRAM 2 MB DRAM 2 MB DRAM
Expandable to 2 or 4 MB 4 MB 4 MB
Operating system RISC OS 3 in 2 MB of ROM RISC OS 3 in 2 MB of ROM RISC OS 3 in 2 MB of ROM
Hard disc None Optional internal 2.5-inch IDE Optional internal 3.5-inch IDE
Keyboard 103 switch, integral 103 switch, integral 103 switch, separate
PSU 10 W 12.5 W 24 W
Colour TV modulator Yes No No
Internal network expansion slot No Yes Yes
Switched joystick inputs 2 No No
Rechargeable battery for the RTC Yes Yes Yes

Other figures used elsewhere on the wiki:

  • Power supply (p. 1-18). The A4000 has a separate cased primary switched-mode supply rated for about 24 W. The A3010 and A3020 supplies are on the main PCB: a transformer whose main secondary gives about 23 V at TP1 (240 V input), stepped down to 5 V by an L4960 (A3010) or L4974 (A3020) switching regulator running at about 100 kHz, with a regulated low-power 12 V supply for the SCART interface and audio op-amp (LK2 isolates it for testing) and unregulated +12 V and -12 V at TP2 and TP3, 50 mA, from a second centre-tapped winding. The ±12 V rails are fused, and a thermal fuse inside the transformer is not to be bypassed; if it fails, the transformer is replaced.
  • DRAM size links (p. 1-20): LK20, LK21 and LK22 on the A3010 (1 MB 1-2, not fitted, 1-2; 2 MB 1-2, not fitted, 2-3; 4 MB 2-3, 1-2, not fitted) and LK31 and LK32 on the A3020 and A4000 (2 MB 1-2 and 2-3; 4 MB 2-3 and 1-2). The Service Manual's references to LK23 and LK24 do not match this table.
  • Plugs (p. 1-20): the plugs table puts the A3010 and A3020 mains input and the A4000 DC power input under one designator, PL1, with the A4000 pins given as 1 +5 V, 2 0 V, 3 -12 V and 4 +12 V. The A4000 main PCB parts list has no PL1: its four-way DC power plug is PL26, part 0800,506 "CONR 4W PLG ST PCB D/PWR" (p. 2-2), and the Service Manual also calls it PL26 (p. 2-3).
  • Interface current limits (p. 1-18): mouse 80 mA, joysticks 50 mA in total, video 50 mA, expansion connector 100 mA internal plus 500 mA external, network expansion 300 mA internal plus 150 mA external.
  • The backup cell is BT2, Acorn part 0817,014, "BAT NI 1V2 280MAH VT PCB", on the A4000 main PCB (p. 2-1), the A3010 1M main PCB (p. 2-5) and the A3020 2M main PCB (p. 2-23). The clock chip is an 8583 (IC5, part 0708,584, for example on the A4000 list, p. 2-2) with a 32.768 kHz crystal (p. 1-2).

What this manual does not contain

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  • No fault-finding or repair procedures; those are in the Acorn A3010, A3020 and A4000 Service Manual.
  • No component-level parts list for the A4000's cased power supply, which is a separate sub-assembly.
  • The engineering drawings listed for Appendix D are not in the scan: it ends with the appendix's one page of text, a blank page and the reader's comment form. The main PCB circuit diagrams are hosted separately (the A3010 set is Acorn's "Adelaide Main PCB" drawing 0194,000, which shows the early board with its CPU daughter card; the A3020 set is the "Heron 'E' Main PCB", drawing 0194,500) for the A3010, A3020 and A4000, three sheets each.
  • No monitor coverage beyond the adaptor cables in Appendix A.

Pages that cite this document

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Download: Acorn A3010 A3020 A4000 Technical Reference Manual.pdf

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