2001: Mac OS X - History of Desktop OSs
The next major OS technology transition at Apple came in 2001, when it introduced Mac OS X with core technologies that Apple acquired with the purchase of NeXT in 1996. Apple initially introduced the brand in 1999 with Mac OS X Server 1.0 which featured the appearance of Mac OS 9 and was a precursor Apple's Mac OS X desktop version that arrived as Mac OS X 10.0 Cheetah.
Mac OS X ran on PowerPC-based Macs until 2006 when Apple announced a hardware transition to x86 and Intel based Apple computers with Mac OS X 10.4. Mac OS X 10.6 "Snow Leopard" was the first OS version to drop support for PowerPC hardware.