Mac OS X, which has UNIX underpinnings different from its predecessor, was introduced in 1999 requiring a PowerPC G3 at minimum, and ported to x86 in 2006.

A quick way to distinguish an Old World from a New World Mac is that all New World Macs have onboard USB ports, while no Old World Macs do. 'New World' motherboard ROMs, with Old World used for System 1-7 on 68k/PPC targets, and New World generally used for Mac OS 8-10 PPC targets, since New World ROMs were stored with the OS, they are available legally from Apple for free online in OS updates. An important divide relevant for Mac emulation is 'Old World' vs. Macintosh computers have always included a platform-exclusive operating system that never had a consistent name. And in 2020 have started a transition from x86 to ARM, further integrating with its more popular iOS mobile spinoff. They switched to x86 in 2007, justifying it with the explanation that PPC failed to be competitive with Intel's Pentium M series. In the early 90s, Apple partnered with Motorola and IBM to combine IBM's POWER with Motorola's 88k to produce the PowerPC (PPC) architecture they used in Macs from 1994-2007, naming some of them accordingly as Power Macintosh. From its launch in 1984 up until 1996, Apple sold Macintoshes with the Motorola 68k family of CPUs. Throughout its history the Macintosh has spanned four CPU instruction set architectures that represent the four commonly known generations. Apple offered the Macintosh alongside its popular Apple II family of computers for almost ten years before those were discontinued in 1993. The original Macintosh was the first mass-market personal computer that featured a graphical user interface, built-in screen, and mouse, eschewing the command-line interface and/or BASIC interpreter that had been the mainstay for home computers since the late '70s.

The Macintosh is a family of personal computers designed, manufactured, and sold by Apple Inc.

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