REX

REX is an on-board virtual option rom library and ram backup device designed by Steven Adolph.

There are a few different types of REX now: REX Classic, REX#, and REXCPM.

REX# and REX Classic provide mostly the same functionality.

• On-board, software controlled, multiple option rom library. Option roms are loaded from a PC over serial cable, and activated/selected/deleted all from software.
  
• On-board multiple full ram image backup & restore. You can snapshot your entire system and restore it later. This can serve as both a recovery after a hard reset or crash or total battery drain, or can be used merely for more storage like ram expansion banks, where you keep more apps & data in multiple ram images than the computer can hold by itself, and switch between them.

The differences are:

REX# is newer and currently sold and supported by the creator. The firmware and software are newer and receiving more updates.

REX Classic provides one feature that REX# does not, which is the Main ROM Management Feature. It allows you to boot from a main rom image on the REX instead of the internal main rom, and manage & modify the main rom image purly from software once the hardware install is done one time. See also FlexROM_100 which adds more hook-up convenience and a 3rd fall-back boot option still without re-opening the case even if you bork both main rom images in the REX.

REXCPM is a very different beast. The headline feature of REXCPM is CP/M. It provides a way to run CP/M on the 100.

It also provides all of the REX# functions, at least outwardly. But the basic REX/REX# functionality isn't really the same because it is a purely volatile RAM device. When it loses power, it loses it's virtual "firmware", rom images, and ram backup images.

You can still use a REXCPM to recover from a hard reset, as long as the computers memory battery hasn't died and as long as the REXCPM hasn't been removed from the computer for more than a few minutes. But if the computer sits on the shelf for more than a few weeks or if you remove the REXCPM from the machine for more than a few minutes, you will need a PC and serial connection and go through the entire setup process again.

The contrast is, the old REX and new REX# are flash devices which never die. They are actually useful for storing rom images and ram backup images, and you can restore from them with nothing else needed even after the computer has fully died. For instance you don't have to bootstrap over serial to get TS-DOS installed, you have it in rom the same as if you had an original TS-DOS option rom.

There is a battery backup for REXCPM, but Steve didn't make it and doesn't sell them. You have to buy the parts and build it yourself. But it adds a battery to the REXCPM and allows the REXCPM to be removed from the computer and still retain it's data for at least a few years.

REX Documentation

Build your own REX Classic

roms