CP/M

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What is M100 CP/M?

REXCPM is an add-on memory card that plugs into the Option ROM socket in a supported laptop, augmenting significantly the amount of memory in the laptop as well as what that memory can be used for. REXCPM changes the way the laptop memory works:

  * REXCPM provides up to 4MB of battery backed SRAM to the laptop.
  * Like REX, REXCPM puts bank switched memory into the OPTION ROM memory bank (1x32k bank)
  * In addition, REXCPM disables (while installed) the internal installed RAM, and replaces it with bank switched memory (2x16k banks)

Why?

CP/M. The main goal of REXCPM is to enable support for Philip Avery's port of CP/M 2.2 onto the M100 hardware. CP/M requires the full 64k address space to be RAM in order to operate, and so a RAM based capability is needed.

RAMdisk. CP/M is a disk based operating system. REXCPM, via the 3 bank-switched memory regions, is able to transform the majority of the SRAM resource into a RAM based, battery backed, ultra fast disk.

...and of course, all of the classic capabilities of REX can be supported using SRAM as well! So REXCPM is really all of the best aspects of REX, combined now with a custom, supported CP/M implementation, opening the door to a wide range of new applications!

Links

REXCPM Information page

Status

  * REXCPM is currently in beta testing.
  * Hardware design and test is complete.
  * Inventory status will be kept up to date at the Ordering page.

Software

example Table

Type	Supported Models	Memory type	CP/M?	Option ROMs?	RAM backups?	PCB2MOLEX Carrier?	Robustness improvements?
REXCPM	M100, T102	Static RAM, 2MB or 4MB	YES	YES	YES	YES	YES
REXsharp	M100, T102	Flash, 1MB	NO	YES	YES	YES	YES

Acknowledgements

I would like to thank those that have contributed to the project:

Philip Avery - for his commitment to this project and for the port of CP/M to the M100

John Hogerhuis - for all his technical support, and for this Wiki resource

Kenneth Pettit - for VirtualT as this project would not have happened without it

Brian White - for his innovative PCB2MOLEX carrier design