The MCX-128 is a memory expansion for Radio Shack’s MC-10 microcomputer
designed by Darren Atkinson. Plugging into the expansion port at the rear of
the computer, it adds a 128k static RAM chip, and a ROM socket that will
accommodate 27128, 27256, 27512, or compatible ROM/EPROMs, and
some logic to tie it all together.
The ROM holds the operating system MCX BASIC, also by Darren.
The memory upgrade along with MCX BASIC allow the MC-10 to use a
client/server package called Emcee Server.
I produced a small run of these recently (30) with Darren’s permission. If you see one with a white solder mask, it’s one I produced.