MacOS

The first several revs of MacOS were even less powerful than the Motorola 68000 dictated.

I assume they eventually got a 32-bit flat memory model.

But things really got interesting in 2001 when Mac OS X (v10.0) shipped, based on BSD/Unix?(!). For full backwards compatibility, [most] Macs still dual-boot with Mac OS 9.2 but that should fade like a bad memory. Then there is the sexy iBook AppleLaptop that it runs on ...

Code name: Darwin

Oddly-enough, there is an x86 port of this. Bootable CD image downloadable from Apple (requires agreement to some arcane legalese) but requires very narrow hardware specs.

Many favorite unix programs have already been ported to MacOS X and are downloadable via a tool called "fink." Although even that has some issues as explained in this article on [MidNightCommander] [local copy]

MacBench and other MacHardware (besides AppleLaptop)