The Acorn Archimedes had the whole OS on a 512KB ROM.
That said, OSs came with a lot less stuff then.
That's only RISC OS 2 though. RISC OS 3 was 2MB, and even 3.7 didn't have everything in ROM as Acorn had introduced the !Boot directory for softloading a large amount of 'stuff' at boot time.
If that is a lot less of things not needed for the specific use case, that is still a big plus.
That's only RISC OS 2 though. RISC OS 3 was 2MB, and even 3.7 didn't have everything in ROM as Acorn had introduced the !Boot directory for softloading a large amount of 'stuff' at boot time.