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Amstrad PCW Hardware Reference (John Elliott)

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PCW Hardware by John Elliott is a technical reference for the Amstrad PCW range, written while he developed the JOYCE PCW emulator. It is not an Amstrad publication. The author's abstract says: "This document describes what I have found out about the hardware of the Amstrad PCW, in the course of writing JOYCE. Some of this has been deduced by me; a lot has come from other sources." The hosted copy is the build dated 26 March 2026: 56 pages with a text layer. The author updates it; the current build is on his site at seasip.info (an August 2026 build had 57 pages with the same sections).

Contents

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Section start pages in the hosted build:

  • 1 General principles, p. 5; 2 Boot ROM, p. 5
  • 3 RAM and paging, p. 5: PCW ("extended") and CPC ("standard") paging modes
  • 4 The screen, p. 6: I/O ports, the Roller-RAM
  • 5 Interrupts, p. 7: timer, floppy controller, serial port and daisywheel interrupts
  • 6 Printer ports, p. 8: the PCW8256/8512/9256/10 printer controller (ports, commands, example sequences, matrix fonts), the PCW9512 printer controller, the PCW9512 PAR port, the CPS8256 CEN port, the standalone CEN port
  • 7 Communications interfaces, p. 14: CPS8256 (Z80-DART registers, Centronics and serial ports), SCA Mark 2 and early SCA interfaces, LocoLink, PCW Linkit, PCWMail, Miracle Technology WS4000, a prototype serial interface
  • 8 Floppy drives, p. 19: the floppy controller and other ports, drive support, the floppy controller probe
  • 9 Hard drives, p. 20: Cirtech Gem, Gem (ATA), Insyder/Hardpak and Flash Drive; ASD PCWHD10/PCWHD20; Timatic Winchester Expansion Box; others
  • 10 Keyboard, p. 24: memory map, keyboard matrix, links, keyboard joysticks, physical connection and wire protocol
  • 11 Pointing devices, p. 26: AMX Mouse, Kempston Mouse, Keymouse, Electric Studio light pen
  • 12 Joysticks, p. 28: keyboard joysticks, Kempston, Spectravideo, Cascade (JoyceStick) and DKTronics interfaces
  • 13 Sound generators, p. 30: DKTronics
  • 14 Networking, p. 30: Multilink, ASD Uninet, Amstrel
  • 15 Scanners and image capture, p. 31: MasterScan, ProScan, digitisers, OCR input
  • Appendix A, dot matrix printer fonts, p. 32 (BIOS fonts and the fonts in LocoScript 1.00-1.20, 1.31, 1.40-1.50 and 2-4, with Z80 code)
  • Appendix B, the LocoLink wire protocol, p. 41
  • Appendix C, the PCW Linkit wire protocol, p. 51
  • Appendix D, the Gem drive system track, p. 54
  • Appendix E, the Flash Drive system track, p. 55
  • Appendix F, the Timatic Winchester Expansion Box partition table, p. 56

What it settles

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The document covers what Amstrad's service manuals leave out: I/O ports, memory paging, interrupts and the protocols of the printer controllers and keyboard. Parts of it that bear on repair:

  • Keyboard (section 10, pp. 24-26): the keyboard's memory map and matrix, the three option links, and the serial wire protocol. Fitting link LK1 puts the keyboard into a test mode in which it sends test patterns continuously and the Shift Lock LED stays lit. The document notes that the physical layout of the matrix is given in Amstrad's service manual.
  • Floppy controller probe (section 8.3, pp. 19-20): the sequence later LocoScript and CP/M versions use to tell an 8256/8512/9512-type controller from a 9256/9512+/10-type, and to detect whether each drive is 3-inch or 3.5-inch.
  • Hard drives (section 9 and appendices D-F): the Cirtech Gem and Flash Drive system tracks and the Timatic partition table.

What this document does not contain

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It describes the hardware as software sees it. There are no schematics, component values or parts lists, and nothing on the power supply or on fault-finding; for those see the Amstrad service manuals listed below. The author notes that some of the content is his own deduction.

Download: PCW Hardware Reference (John Elliott).pdf

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