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.
Installing 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
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.
REX2 will be available in the near future. In addition to the 1MB of flash, it also provides 128 kbytes of SRAM. This SRAM is included to allow for an all-RAM mode of operation, mainly for CP/M support. This activity is being done in conjuction with the development of Model T CP/M, via the MTCPM mailing list.
REX2 will require a more detailed installation. Specifically, the SRAM chip needs 3 wires soldered from the motherboard. Also, I expect the actual installation of REX2 to be slightly more difficult, since the 3rd chip causes the underside of REX to be non-planar, making REX2 a bit more difficult to seat properly in the socket.
REX2 also includes support for 2MB of flash. If I can find some of those chips, I will make use them on REX2. Why not?
Since this will be of limited interest, I will make these available to anyone interested as a side activity to the main REX product.