System 7 released (1991)
Unsupported Macs: Original Mac (7 years), Mac 512K (5 years)
Mac OS 7.6 (1997)
Unsupported Macs: Mac II (10 years), SE/30 (8 years), PowerBook 100, 140 (5 years)
OS 8 (1997)
Unsupported Macs: Mac IIfx (7 years), Performa 560 (3 years), PowerBook 180c (4 years)
OS 8.5 (1998)
Unsupported Macs: Quadra 840 AV (5 years), Quadra 610 (5 years), PowerBook 550c (3 years)
OS 9 (1999)
No new incompatibilities
OS 9.2 (Late 2001)
Unsupported Macs: Power Mac 9600 (4 years), Power Mac 6100 (7 years), PowerBook 3400 (4 years), PowerBook 1400 (5 years)
OS X (2001)
No new incompatibilities
OS 10.1 (2001)
No new incompatibilities
OS 10.2 (2002)
No new incompatibilities
OS 10.3 (2003)
Unsupported Macs: Power Mac G3 233 (6 years), Power Mac 333 (5 years), PowerBook g3 266 (4 years)
OS 10.4 (2005)
Unsupported Macs: Original iBook (6 years), Original iMac (7 years)
OS 10.5 (2007)
Unsupported Macs: Original PowerBook G4 (6 years), iMac G4 800 (5 years), Power Mac G4 400 (8 years), Power G4 733, Quicksilver (6 years)
OS 10.6
Unsupported Macs: Power Mac G4 867, Quicksilver (2001), PowerBook G4 1.67 (2005), iMac G5 (2004), G5 PowerMac Dual Core 2.5 GHz (2005)