I believe booting from HD, CD or Fireware are the acceptable bootable devices in NewWorld macs, whereas OldWorld macs could boot from SCSI,CD or PCMCIA. I think anything post-PowerPC can boot from wherever.
I'm going to try to attempt this again this weekend using a CD. I can, in theory, make an ISO of 9.2.2, trade out the Mac OS ROM file with the 10.2.1 version, then see if the CD will boot. It's clear that this version of the Mac OS ROM removes the MacRISC2 limitiation, instead allowing all "MacRISC." machines to boot from this version of ROM. From what I know of the boot process, the following happens:
1) OF (OpenFirmware) recognizes and orders devices it knows about.
2) OF Looks at each device, ordered by first what you selected (stored) in Startup Disk control panel as your preferred device, and then opens that device looking for a Mac OS ROM file.
3) Once a suitable ROM file is chosen, its contents are copied into a location in memory to be parsed and run.
4) The program runs, loading the bitmap of the happy mac, and then proceeds with the boot process, booting from the already-valid device selected by OF.
If i'm wrong here, let me know.
I'm going to try to attempt this again this weekend using a CD. I can, in theory, make an ISO of 9.2.2, trade out the Mac OS ROM file with the 10.2.1 version, then see if the CD will boot. It's clear that this version of the Mac OS ROM removes the MacRISC2 limitiation, instead allowing all "MacRISC." machines to boot from this version of ROM. From what I know of the boot process, the following happens:
1) OF (OpenFirmware) recognizes and orders devices it knows about.
2) OF Looks at each device, ordered by first what you selected (stored) in Startup Disk control panel as your preferred device, and then opens that device looking for a Mac OS ROM file.
3) Once a suitable ROM file is chosen, its contents are copied into a location in memory to be parsed and run.
4) The program runs, loading the bitmap of the happy mac, and then proceeds with the boot process, booting from the already-valid device selected by OF.
If i'm wrong here, let me know.