REXCPM

From Bitchin100 DocGarden
Jump to navigationJump to search

REXCPM.PNG

What is REXCPM?

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

Philip Avery's M100 CP/M 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.

Documentation

Software

Utilities

Backup and Restore

A tool is available for backing up or restoring REXCPM memory contents to TPDD. Some of the REXCPM SRAM is dedicated to CP/M while other memory is dedicated to REX functionality. This tool allows you to select:

  * Backup or Restore process
  * REXCPM or CP/M memory regions
  * Serial port speed - 19200 8N1 or 76800 8N1 "Large Packet"

The tool uses the standard RS-232 port on the M100. Standard TPDD clients can operate at 19200 baud, but LaddieAlpha is capable of operation at 76800 baud, and also able to support large packet sizes, both of which help to speed up the process.

Backup/Restore processes can take some time; use this table for guidance.

Process Memory size Duration Duration
REXCPM 2MB 19200 9 min
REXCPM 4MB 19200 9 min
CP/M 2MB 19200 25 min
CP/M 4MB 19200 60 min
REXCPM 2MB 76800 3 min
REXCPM 4MB 76800 3 min
CP/M 2MB 76800 8 min
CP/M 4MB 76800 20 min


D2RC (Disk-to-REXCPM) is the bootstrap utility. Its job is to load a REXCPM "ROM" image into REXCPM. Here's the software:

PUtility Version File
D2RC 1 File:D2RC.DO
  Instructions
  * load D2RC.DO into the M100 using a terminal program on PC (lots of ways to do this)
  * enter BASIC and type RUN"D2RC.DO
  * The loader will load up the machine language routine into ALTLCD, and begin to execute
  * At the prompt, enter the full file name of the ROM image you want to load.
    Note:  A full image includes an erased directory and is 32k long.  An upgrade image is code only and is 28k long.
  * Ensure that a TPDD client is attached to the serial port, and that the desired file is directly accessible.
  * Once entered, D2RC will attempt to load the named file into the default OPTROM block of REXCPM.
  At this point, REXCPM should have a new "ROM" load for REXCPM (and possibly a blank directory). 
  CALL 63012 to start REX.

Initialization of REXCPM

Installation and Set Up

Installation information for Model 100 here ----> M100 install

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