> Also, by Apple eventually abandoning backwards compatibility, it was able to migrate Macs to different better processors four times. 68k -> PPC actually did

> Also, by Apple eventually abandoning backwards compatibility, it was able to migrate Macs to different better processors four times. 68k -> PPC actually did not break backwards compatibility at all. They realized it they had to make it good for the transition to work, so they built emulation right into the OS. A well-behaved app made for a 1984 Mac will run unmodified on the last version of old Mac OS, and on Mac OS X up to 10.4 under the Classic environment, that's over 20 years of compatibility. Apple could have maintained this level of compatibility until today, but they choose not to.