CPC-series Technical Details and Trivia


  • an expansion port for disk drives - 50-pin male edge connector. On Schneider models, this was replaced by a standard Centronics port.
  • a printer port (7-bit) - 34-pin male edge connector.
  • a single joystick/paddle port, incompatible with other systems, but joysticks come with a second port to allow daisy-chaining - 9-pin DB9 plug.
  • a monitor output socket (also used for TV modulators MP1 or MP2) - 6-pin round DIN.
  • a stereo headphone jack - 3.5mm - not present on some early CPC464s
  • a power supply socket (from either the monitor or the TV modulator) - 5V DC.

Technical Facts

  • The 3" Hitachi floppy drives are 40-track and the disks store 180K (178K in AMSDOS format) per side, or 360K in total. The drive interface is standard "Shugart", allowing Amstrad CPCs to use 3", 3.5", or 5.25" floppy drives as their second drive if required.
  • The CPC464 monitor (either green screen model GT64 or colour model CTM640) contains the computer's power supply. If the computer is to be used with a television, a seperate TV modulator (MP-1 for the CPC464 or MP-2 for the CPC664/6128) must be used which also contains a power supply for the computer. The monitors were different for the CPC664 and CPC6128 than the CPC464 because they included a 12V power supply for the floppy disc drive (and other accessories including the CT-1 Clock Timer) as well as the 5V power supply for the computer. The CPC664 monitor models were the green screen GT65 and the colour CTM644. Later CPC464s were sold with these monitors after Amstrad had sold out of their GT64 and CTM640 stock. For this reason the 12V power outlet from these later monitors was a socket to support a cable from the computer. All other connectors were hard-wired from the back of the monitor.
  • The CPC664 had the same output sockets and ports on the rear with the exception that the 664 and 6128 came with an additional 12V input needed to power the built-in floppy disk drive.
  • A rare accessory for owners of the CTM-644 monitor (supplied with the CPC6128) was the CT-1 Clock Timer. This was a clock radio that was designed to fit underneath the monitor, much like hi-fi separates units of the era that stacked on top of each other. The CT-1 was powered via the 12V output on the front of the monitor, and provided an LCD clock, alarm, and 3-band FM/MW/LW radio.
  • Another accessory for use with the CTM-644 monitor was the MP-3 TV tuner module. Like the CT-1 this would sit underneath the monitor itself as a 'separates' unit. It was used for viewing analogue TV channels on the CTM644 monitor. One downside to the design of the MP-3 is that there is no switch to easily select TV mode or computer mode - you had to manually unplug the 12V and RGB cables to switch from TV to CPC.


Hover your mouse over the circuit board for a description of the components

Component details reproduced with friendly permission from Sothius' Home, www.sothius.com


  • During development, the choice of using the Zilog Z80 CPU instead of the 6502 was interesting. Project "Arnold" was well behind schedule, and Locomotive Software who had been commissioned to write the BASIC interpreter for the new system (the CPC464) reckoned it would take 8 months to write BASIC for the 6502, but much less time if it were to use a Z80. Given that so little hardware had been completed to date it was decided that MEJ (the hardware firm) would start from scratch on building a Z80-based system.
  • The CPC464 was originally planned to be based on the 6502 microprocessor, but was changed around the time of the first Arnold prototype because at that time Locomotive BASIC was available only on the