AppleCare’s Knowledge Base includes several relevant articles on the topic:
- System Software: Version Matrix, System 6.0.x to 7.0.1
- System 7.1 through Mac OS 7.6: Compatibility With Macintosh Computers
- Mac OS 8 and 9 Compatibility with Macintosh Computers
- Mac OS: Versions, builds included with PowerPC Macs (since 1998)
- Mac OS X Versions (builds) included with Intel-based Macs
My favorite tool for finding a quick answer to this question is Ian Page’s awesome MacTracker, a comprehensive collection of vital information about every model of Macintosh that is available as a free Mac OS X or Windows application, or via a web site that’s optimized for viewing on an iPhone or iPod Touch.
Now, as for which version of the Mac OS is optimal for your model of Macintosh, well, that’s beyond the scope of this article. The folks over at lowendmac.com have a number of helpful articles on this topic, though.