I built my first CT home automation system on CP/M. Had a few North Star boxes — S-100 bus. Built I/O boards with discrete chips 74xxx. Had an entire board that was a real-time clock. Got it all done with 64k. Early 80s brought about ramdisk boards to replace floppy drives. DRC had a few. It was rather easy to take a 256k ramdisk board, upgrade the chips and viola you had a 1 meg ramdisk to boot. I even ran ads in Byte magazine one issue. Retired it all in 2006. 2007 brought me to Florida and its all on a Zotac running Ubuntu linux. Python.
My S-100 box was equipped with those “more reliable” North*Star hard sectored floppy drives! Z-80 of course and full static memory, a handful of serial ports and a bunch of ham radio specific hardware. 20 slots filled up fast!