Apple

You could use a 1GHz TiBook. Those will still run 9.2.2. I have an 867MHz and a 1GHz TiBook, and they're great mobile OS 9 workstations.

ClassicHasClass wrote: You could use a 1GHz TiBook. Those will still run 9.2.2. I have an 867MHz and a 1GHz TiBook, and they're great mobile OS 9 workstations.

That's the most powerful laptop that can boot OS 9. (The best desktop capable of booting OS 9 is the G4 1.25 GHz MDD.)
But all PowerPC macs can run the Classic environment in OS X 10.4.11.
The vast majority of programs work in Classic; the only one I remember that benefitted from booting OS 9 was SuperCollider 2/3.

robespierre wrote: But all PowerPC macs can run the Classic environment in OS X 10.4.11.

Not exactly. Only G3/G4/G5 machines officially could run OS X. Machines based on the 601/603/604 PowerPC CPUs were limited to various versions of the classic MacOS. (Sure, there were patches and workarounds that would let OS X run on some of these older PowerPCs, but I don't think anyone would find that to be much fun, especially if trying to run Classic on top of OS X.)

The closest thing to it that is true is that all PowerPC Macs that support OS X 10.4.11 or earlier versions of OS X or MacOS can run some version of the classic MacOS, either directly booting into a supported version of the classic MacOS or by running the Classic environment in a supported version of OS X.

(Sorry: I didn't mean to be pedantic, but hey, this is a vintage computing forum. Are there groups with higher percentages of pedants than vintage computing forums? )

The vast majority of programs work in Classic; the only one I remember that benefitted from booting OS 9 was SuperCollider 2/3.

Sure, they'll work, and that's why 10.4 is my preferred version of OS X on PowerPC. But OS 9 on the raw metal is a lot faster, and some apps don't work quite right in Classic (mostly games).

Classic is still heaps better than any emulator, of course, not least of which being the excellent system integration.

For the record, I run SuperCollider 3.4 on 10.4, and I intentionally bought an MDD new back in the day because it could still dual boot. It has a Sonnet dual 1.8GHz G4 in it now.

Interesting! Have you tried SuperCollider 2? I think 3.4 was a total rewrite and wasn't the same codebase as 2/3.0alpha.
I just remembered that another program that didn't like Classic was TC Spark. And certain graphics applications had funky display redraw issues (Illustrator, etc). It can certainly be advantageous to be able to boot into OS 9.