When it comes to famous operating systems for the Z80 and similar Zilog processors, the first and maybe only one to come to mind is CP/M, which was even made its presence known on the dual-CPU (8502 and Z80) Commodore 128. Yet Zilog also developed its own operating system, in the form of the comprehensively titled Z80 Operating System with Relocatable Modules and I/O Management (Z80-RIO for short). With limited documentation having survived, [Ralf-Peter Nerlich] has set out to retain and recover what information he can on RIO and the associated Programming Language Zilog (PLZ) after working with these systems himself when they were new.
A Zilog MCZ 1/20 system from around 1979. (Credit: Herb Johnson)
Perhaps unsurprisingly, neither Z80-RIO nor PLZ were targeting the regular consumer market when they were brought to market in the late 1970s, but were part of Zilog’s focus on industrial markets, as well as laboratories and elsewhere that could benefit from a versatile, programmable computer system for control and automation.
As part of an integrated hardware/software solution, Zilog released a series of computer systems, such as the MCZ 1/20 of which a number of examples survive today. Herb Johnson’s collection and restoration projects provide a good overview of not only the base systems, but also the expansion cards available for these systems. Right along with the ..
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