Editing Amstrad CPC (section)

===Expansion===
[[File:Amstrad CPC646-IMG 7196.jpg|thumb|Back of the case of a CPC 464, with the mini-jack, joystick and printer ports.]]
The hardware and firmware was designed to be able to access software provided on external ROMs. Each ROM has to be a 16&nbsp;KB block and is switched in and out of the memory space shared with the video RAM. The Amstrad firmware is deliberately designed so that new software could be easily accessed from these ROMs. Popular applications were marketed on ROM, particularly word processing and programming utility software (examples are Protext and Brunword of the former, and the MAXAM assembler of the latter type).

Such extra ROM chips do not plug directly into the CPC itself, but into extra plug-in "rom boxes" which contain sockets for the ROM chips and a minimal amount of decoding circuitry for the main machine to be able to switch between them. These boxes were either marketed commercially or could be built by competent hobbyists and they attached to the main expansion port at the back of the machine. Software on ROM loads much faster than from disc or tape and the machine's boot-up sequence was designed to evaluate ROMs it found and optionally hand over control of the machine to them. This allows significant customisation of the functionality of the machine, something that enthusiasts exploited for various purposes.<ref name="Amstrad CPC ROM expansion">{{Cite web|url=http://8bit.yarek.pl/hardware/cpc.rom/index.html|title=ROM :: Amstrad CPC -- 8bit Projects For Everyone|website=8bit.yarek.pl|access-date=1 November 2009|archive-date=8 August 2009|archive-url=https://web.archive.org/web/20090808173010/http://8bit.yarek.pl/hardware/cpc.rom/index.html|url-status=dead}}</ref> However, the typical users would probably not be aware of this added ROM functionality unless they read the CPC press, as it is not described in the user manual and was hardly ever mentioned in marketing literature. It is, however, documented in the official Amstrad firmware manual.

The machines also feature a 9-pin [[Atari joystick port]] that will either directly take one joystick, or two joysticks by use of a splitter cable.<ref name="464 Tech spec"/>