[masswerk]

> so there was no possibility of loading the OS from volatile storage.

There are exceptions to this rule: Sharp was known for their concept of "clean computers" (MZ series and X1), which came only with a simple monitor in ROM, while at the same time featuring just a cassette drive to load a BASIC interpreter (of which there were several flavors) from.

[ikari_pl]

And Amstrad PCW had boot code in the printer controller, to save on ROM prices :D, and booted from a floppy only (by default to a CP/M as well)