Also i have summarised the PX4 manual with this CP/M command reference.
Extra Info:
A bunch of useful programs for use on and with the px4 can be
found at ftp://ftp.discordia.org.uk/pub/discordia/cpm such as EPROM images for the utilities, a cp/m emulator, filink file transfer tools, and assorted other utils.
Hopefully more information will follow as time allows, please email any requests for information to madmitch@discordia.org.uk and i will try to find it and post it up.