REX

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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 provides support for up to 16 in-circuit selectable option roms. That means, you can have 16 different software packages on one Option ROM, and select between them without physically unplugging anything.

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.

An additional feature is a facility for freezing/thawing up to 16 RAM images to/from flash. 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!

For advanced users, 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 is available exclusively through Club100.

REX installed.jpg

REX Overview PDF

REX Documentation

REX Software and Utilities

REX Validated ROM Images for M100/T102

REX Manager

REX comes pre-programmed with REX Manager software. REX Manager allows you to pick which of the ROM or OS images is the one currently in use, and also supports management of RAM images.

REX Manager operates "behind the scenes" to make sure the currently selected Option ROM image is automatically enabled on every power cycle. This is an impressive trick since REX does not receive power while the laptop is off (unlike the RAM memory circuit).

REX Manager is started by running the program REXMGR.BA from Menu.

Advanced BASIC ROM Replacement Mode (OPTIONAL)

For users with the do-it-yourself spirit, an optional feature of REX can be enabled.

With a single wire soldered in place, REX permits BASIC ROM replacement!

This means that you can disable the built-in BASIC/TEXT/TELCOM ROM on your motherboard and replace it with a specific block of REX flash memory. Typically, this will be the same BASIC/TEXT/TELCOM ROM image we know and love, with a few changes. So, you can upgrade your Model T with little tweaks like Y2K, the lomem patch, new character sets, put your name on the main menu, etc.

Installing REX Manager - It's Easy

From a cold restart, power cycle the laptop and the simply type

CALL 63012

will install the REX system.

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

Additional Utilities

REXUPG.CO is a utility that allows the user to upgrade the internal REX Manager software.

REXMR.CO is a utility that allows the user to program upgraded main rom images into REX for use in "ROM Replacement" installations.

Future Roadmap

REX2 will be available in the near future. It provides additional blocks of SRAM, allowing an all RAM mode of operation, for CP/M support.


Rel. 4.3 Beta testing: bug reports/fixes

I should not have sent out the "4.3 beta" a few weeks ago as it was too alpha.

I found a number of bugs that were subtle and affected stability. Now that those are resolved, and the TPDD routines are robust to TPDD problems, I now have a candidate final load. All the features I have considered have been implemented.

R4.3b supports M100/T102 only right now. I will have a T200 R4.3b shortly.

Tested drive targets include: NADSbox, LaddieCon, TPDD-1, TPDD-2


1) fixed in 4.3 - timeout of TPDD 1/2 - after loading an image, a command response times out at the end...need to extend the timeout delay.

Rel. 4.2 Beta testing: bug reports/fixes

1) DONE R4.3 - found error in code - Year bug - the year data is not correctly preserved by REX when RAM images are saved and loaded. Solution - implement a mechanism that maintains the year data properly.

2) directory bug with entry for block 31 - it appears that the name entry for block 31 is not displayed correctly, investigation continuing.

3) DONE R4.3 - sound is disabled - sounds - currently REX uses audible clicks to indicate progress, which can be annoying. Solution - disable audio, replace with some other mechanism.

4) DONE R4.3 - directories are now sorted in descending order of date/time - directory order - current directory entries are displayed in order of block number, which is problematic since this causes reordering whenever REX garbage collection forces an image to be moved from one block to another.

5) DONE R4.3 - Overall stability - Identified and fixed two subtle bugs relating to interrupt handling and bank switching.

6) DONE R4.3 - Robustness for TPDD routines - major rewrite of the TPDD routines in 4.3.

7) DONE R4.3 - included choice for refresh or revert - Restore from current ram image - there is no easy way to restore from the current backup image. Solution TBD. work around is to copy the backup image to a new block, and then install that image.

8) DONE R4.3 - non-blank block recovery - it is possible that REX attempts to copy an image to a non blank block. This situation is indicitive of a problem with the system since this should never happen. If it does occur, the system gets in a deadlock condition. Solution - make sure REX has no bugs in this functionality first, but an option to "name" or "delete" the offending block would be a nice safety system.

9) DONE R4.3 - enter function displayed on line 2 - state function of <enter> for cursor item on screen somewhere - don't leave it to memory only

10) DONE R4.3 - <TAB> is included in top line now - indicate <tab> is used to toggle groups.

11) DONE R4.3 - order is now RAM ROM OS (SYS) (SYS is a superuser feature) - change group display order to avoid tabbing past OS type.

Enhancement Requests

StatusDescriptionRequester / Date
UnknownSupport import of file from frozen RAM image to the thawed RAM image. RAM images can be used in a way similar to subdirectories. Therefore it is useful to be able to retrieve files from frozen RAM imagesJhoger 08:16, 16 April 2009 (PDT)
Done R4.3Suggestion: make the TAB order OptROM, RAM image, Main ROM since Main ROM switch will be significantly less used. (order is now RAM ROM OS SYS)Jhoger 19:54, 18 April 2009 (PDT)
Done R4.3Add a visual progress indicator for flash functions.Sadolph 04:36, 19 April 2009 (PDT)
unknownSupport for TPDD-2, for drive 1: (0: is supported).Sadolph 04:36, 19 April 2009 (PDT)


nb: to put a username+datestamp just type 4 tildes ~~~~