REX

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For Owners

Own REX, need help Getting Started?

REX Quickstart guide


Hi- Keep in mind the following-

  • For current release 4.5, do not fill REX beyond 1/2 full (12 remaining blocks must be free).
  • make sure you put real data into the default BACKUP entry in RAM group


And, read the newly added user guide from Jonathan Rose!

cheers, Steve

What Is REX

REX is completely plug and play flash memory upgrade. REX plugs into the Option ROM slot, with no soldering or necessity to open the laptop case.

REX gets it's name by being a cross between my other flash memory device, ReMem, and the original OPTION ROM (RAM) memory card, EXTRam.


The primary features of REX are:


  • REX allows for quick and easy switching between OPTION ROM images. Once the binary software images are loaded into REX, the user can easily jump back and forth between different applications. 16 OPTION ROMs may be loaded, stored and used.


  • REX provides the ability to backup and swap working RAM images. At the press of a key, your current RAM contents are saved in REX. Furthermore, you can reload any saved RAM image for use. This creates a library of RAM images, which has a number of uses. This offers an easy way to quickly backup all RAM to flash, or switch between multiple snapshots of RAM. This is similar to the "fast switch environments" on Remem: it is like having multiple laptops in the same case! 16 RAM images may be stored.


  • REX includes an interface to TPDD devices (like TPDD, NADSbox, LaddieCon etc) for loading and saving binary images to external storage.


In addition, REX is in-circuit, software reprogrammable. That means you can change, patch, or replace an Option ROM image without any special hardware or physically unplugging REX.


For advanced users, REX provides some additional features:


  • REX distinguishes between traditional OPTION ROM software, and alternative OS software which runs from the option rom memory location. This allows for some interesting future capabilities like CP/M or a FORTH based system.


  • REX also supports "Main ROM Replacement". This means that, with the addition of a single wire, the main rom on the laptop may be replaced by a version stored in REX. This allows for flash-upgradeable main ROM images, to support patches, custom Menu and character sets, LOMEM patch, Y2K patch etc.


REX may be installed in Model 100 and Tandy 102 currently. Tandy 200 support is not yet available but is in development.



REX is available exclusively through Club100.


REX installed.jpg

REX Overview PDF

REX Overview

REX Hardware Installation

REX Manager User Guide

REX Software and Utilities

Main ROM Replacement

REX Validated OPTROM Images for M100/T102

REX2 - custom REX for CP/M support

Software Installation of the REX System- It's Easy

In order to initialize the laptop to use REX, you must install the REX system. From a cold restart, power cycle the laptop and then simply type


(for M100/T102)

CALL 63012


(for T200)

CALL 61167,2

to install the REX system, which installs one hook in the timer, includes two short programs.

  • first, an invisible file called RXHOOK which contains a special machine language routine that interacts with the timer hook in the laptop, to ensure that REX is properly configured on power up.
  • and a visible basic program called REXMGR.BA. This program contains a short embedded machine language routine that starts the REX Manager software on command.


You should see a program in the Menu called REXMGR.BA. Running this program will always start the REX Manager software.


After REX Manager is installed, issuing those same commands won't re-install the system, but you will be directed to the Active OPTROM image software instead, just like you would expect if you had a normal option ROM installed.

If the REX system should somehow become de-installed (like on a cold restart) simply re-install it by repeating these instructions.

Important Note for First Time REX Installation and Use

IMPORTANT! For brand new REX installations, where REX has been unused, the user must replace the default "backup" RAM image stored in REX, with a real backup image. Simply start REX Manager, move the cursor over the directory entry for "backup", and press <ENTER>. Select <Y> when prompted to "Refresh backup?". This puts a fresh RAM image for your specific machine into that entry.