Now here's an idea I hadn't thought of for bare-metalling... Emulators. Right? Why run an emulator atop an OS?
There're some great thought-points in the commentary, here... I'm no emulator-designer, and barely even use emulators... so I can't vouch for anything said.
I have, however, run VirtualPC on a 1GHz PowerBook-G4 and... running WindowsXP was *doable*; booting took about 20min, then... I used it for CircuitMaker2000, which... was I think written for Windows95/98... and... it was atrociously slow (but functional enough to slowly design several circuit boards). Were it a Win98 machine with CM2K, I think a 100MHz Pentium woulda been plenty. So, I think a 20:1 slow-down is a reasonable estimate... (1GHz G4 => 50MHz Pentium).
So... how much of that was due to OS overhead...? How much was due to MAC-OS overhead, and then, again, how much more of that was due to WinXP overhead...? If I'da done Win98, would it've been significantly faster? Who knows... Maybe I'll rerun those experiments when I acquire my "new" PBG4 replacement.
Regardless, it'd be hard to dispute that running a bare-metal emulator should certainly be faster than running one atop an OS...