Interesting. I thought the new MacOS was unix-y? But I never owned a Mac back then so not sure. For me Windows 2000 is the pinnacle. It doesn't crash (often), supports most of the games I played then, and I like the UI design.
OS X and later are derived from NeXT Step, which makes it derived from BSD. And thus, UNIX-y. Macintosh system software versions less than 10 are Apple original development. The earliest versions were designed for hardware with only 512 or 128 kilobytes of RAM and without physical support for protected memory.
Unfortunately, backwards-compatibility requirements prevented the addition of process memory isolation before OS X. One result of not having this protection was that an application with a memory bug could overwrite memory location zero(the beginning of a critical OS-only area), or any other memory area, and then all bets were off. Some third-party utilities, such as Optimem RAMCharger, gave partial protection from this by using the processor's protected mode, and also removed the occasional need for users to manually set the amount of memory allocated to a program. However, many programs were not compatible with these utilities.
