a series of computers that defined the professional workstation for OS X users for many years. In June 2003 — 15 years ago this month — Steve Jobs took the wraps off its successor, the Power Mac G5.

In January 2006, the first Intel Macs were announced. We’ll deal more with that anniversary in a year, but for now, it’s worth walking through the final full year of PowerPC Macs. Transitions happen ...