IBM PC/AT (1984)
What? No IBM PC or XT? Yes, we know those systems began the PC era. But the pace of change was so fast back then, and the power of Intel 8088 and 8086 processors was so slight, that the more muscular Intel 80286 made "plain PCs" obsolete almost overnight. The AT's memory, for example, topped out at 16MB as opposed to the PC's toylike 640K. The first model debuted at 6 MHz, but an 8 MHz model quickly followed. The AT was discontinued in 1990, four years into the Intel 80386 era.