[kazinator]

> UNIX breaks down quickly without multiple fake single address spaces for each program.

So do MS-DOS, Mac OS < 9, and others: any non-MMU OS.

> Yes, and with unrestricted memory access, one program can crash the entire system.

That's true in any system with no MMU that runs machine-language native executables written in assembly language or using unsafe compiled languages.

Historically, there existed partition-based memory management whereby even in a single physical address space, programs are isolated from stomping over each other.

https://en.wikipedia.org/wiki/Memory_management_(operating_s...