I had a theory that OS 9 would not understand the G5's SATA bus, but it might understand the regular IDE bus (normally used for optical drive).
However moving everything to the IDE bus did not deliver any greater results.
I wonder what ATA chip the G5 has. It is LBA 48-bit (despite the fact that it's only used for optical drives - it works fine with large IDE hard drives as well, you can even use Master/Slave if you can mount the extra drive somewhere and split the power rail). Equill said that only ROM 10.2.1 (which I have been using) will support LBA 48-bit.
It really seems like it just starts trying to load OS 9, but OS 9 gets massively confused and aborts all the way to the blinking system folder icon, where Open Firmware takes over again and tries to locate a suitable replacement System to boot from.
I think the G5 processor or bus or something is just too crazy different for this to ever work. However I think there could be success with G4 models that dropped OS 9, such as later eMacs, iMac G4s, PowerBook G4s, and maybe even iBook G4 or Mac Mini G4. I think these are all close enough, and often they didn't change much in terms of chipset. For example, TAS3004 was used on almost every Mac from the era and I'm sure at least one of those booted OS 9 natively, therefore OS 9 supports TAS3004 sound.
Biggest problem I see is USB going dead due to the lack of USB 2.0 drivers, which means no keyboard or mouse. This could be resolved on the MDD G4 with a PCI card. Also PowerBook G4s and iBook G4s still used ADB internally for their keyboard and trackpad so those would still work. (Hack idea: turn internal trackpad connection into external ADB port)
However moving everything to the IDE bus did not deliver any greater results.
I wonder what ATA chip the G5 has. It is LBA 48-bit (despite the fact that it's only used for optical drives - it works fine with large IDE hard drives as well, you can even use Master/Slave if you can mount the extra drive somewhere and split the power rail). Equill said that only ROM 10.2.1 (which I have been using) will support LBA 48-bit.
It really seems like it just starts trying to load OS 9, but OS 9 gets massively confused and aborts all the way to the blinking system folder icon, where Open Firmware takes over again and tries to locate a suitable replacement System to boot from.
I think the G5 processor or bus or something is just too crazy different for this to ever work. However I think there could be success with G4 models that dropped OS 9, such as later eMacs, iMac G4s, PowerBook G4s, and maybe even iBook G4 or Mac Mini G4. I think these are all close enough, and often they didn't change much in terms of chipset. For example, TAS3004 was used on almost every Mac from the era and I'm sure at least one of those booted OS 9 natively, therefore OS 9 supports TAS3004 sound.
Biggest problem I see is USB going dead due to the lack of USB 2.0 drivers, which means no keyboard or mouse. This could be resolved on the MDD G4 with a PCI card. Also PowerBook G4s and iBook G4s still used ADB internally for their keyboard and trackpad so those would still work. (Hack idea: turn internal trackpad connection into external ADB port)