Thinking about this. Could we produce a G3 ‘Rominator’ that has built-in USB support and other improvements, like holding down option at startup to choose a boot device?
Depends on how much space is free in the ROM compared to how much code is required for USB support and Startup Manager (boot picker). First thing to do is extract the code from New World Open Firmware and get it to work in Old World Open Firmware. Then we can see if it will fit. If it can't fit, then the Rominator idea can still work to store a small amount of code that can load more code from an Open Firmware accessible disk.
The Open Firmware part is probably the easiest and would probably be sufficient for OS X. I don't know anything about the non-Open Firmware parts or if some non-Open Firmware code is required to select a OS 9 boot device. Can Old Word Open Firmware be used to change the OS 9 boot device? As far as I know, the only thing it will boot is
/AAPL,ROM
. Maybe there's a PRAM value that can be modified.
@elliotnunn's GitHub projects deal with New World ROM files (tbxi) but I don't think they're applicable to Old World ROMs?
The Startup Manager is mostly handled by the
multiboot
package in Open Firmware and there's a
multi-boot
word. Open Firmware of the B&W G3 looks for the option key but then it ignores the result and skips booting from
multiboot
. Maybe Apple skipped that code because it wasn't working well enough in that version of Open Firmware (3.1.1) or maybe I'm misinterpreting the code? Maybe the Yikes G4 has newer Open Firmware? I don't have a ROM dump from Yikes so I can't check that. The earliest post B&W G3 Open Firmware dump I have is for 4.1.9f1 from an iMac. That version appears to correctly call
multi-boot
when the Option key is held down.