REX

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

REX Documentation

Build your own REX

A few more ROMs

These are mostly the same as the roms zip file from the REX docs.

• Disk+2.0 is from a commercial rom I found in one of my machines. It hasn't been uploaded anywhere else yet that I know of.
• MFORTH is a newer version than in the zip file.
• AZ23 and AZ24 are AlphaZ 2.3 and 2.4
• HOOT2C is from an EME Systems "OWL" (Online Weather Logger) machine.

Some roms in the roms zip from the REX docs have been patched to work better with REX, so generally you want to use these copies specifically rather than other copies of the same roms.

REX Hacking

Work in progress. Current version c8
Version c8 is not tested yet.

This is a version of REX1 that I have modified to address a few things with the original REX1:

• Let the pcb manufacturer pre-castellate the pcb edge contacts, so the pcb comes from the manufacturer almost ready to use, needing only a little light sanding to clean up the panelization break-off points.
• Provide a practical and safe way to supply 5vdc to the board during CPLD programming.
• Provide a practical and safe way to hold PORT_EN high during CPLD programming.
• Fit into a 3d-printed carrier that fits the option rom socket.
• Cosmetic clean up: remove un-used component footprints, arrange remaining components into a symmetrical arrangement, remove the 0-ohm resistor, silk screen text.

• PCB: https://oshpark.com/shared_projects/DKF7eN1c
• BOM: https://www.digikey.com/short/pbcqtn
• Sled: https://www.thingivrse.com/thing:3723135

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Version c6 is tested and verified.
The electronics have not changed between c6 and c8.

The c6 photos show the new 5v and PORT_EN connections for the initial CPLD programming.