NetBSD refuses to boot on iMac G4 USB 2.0

[Thomas Sirack <tsirack%protonmail.com@localhost>]

Hello everyone,

I recently tried installing NetBSD on an iMac G4, but cannot get it to boot successfully, if at all. More specifically, the machine in question has the model ID PowerMac6,3 and is the 15 inch USB 2.0 version of the iMac G4. It has a 1 GHz PowerPC G4 processor, 512 MB RAM, and an 80 GB hard drive.

I initially partitioned the HDD from a Mac OS X DVD. However, because my particular G4 model does not support booting into Mac OS 9, I had to use the Terminal application on the CD alongside the "diskutil" command to format the drive with OS 9 drivers installed. I had made a 10 MB HFS+ partition for the bootloader file, ofwboot.xcf, to reside in, and copied it into that partition.

Afterwards, I finished partitioning off of the NetBSD CD using "pdisk". In doing so, I changed the partition type of the bootloader partition on the hard drive from "Apple_HFS" to "Apple_Bootstrap". I did this because some PowerPC Linux distributions require their bootloader to reside in one of these "bootstrap" partitions.

I then formatted the root partition and installed NetBSD as per usual. However, rebooting into Open Firmware to try and boot NetBSD from the hard drive, I tried the following command:
boot hd:9,\ofwboot.xcf

(For the rest of this email, partition #9 is the bootloader and partition #11 is the NetBSD root partition.)
This command, however, did not work, with Open Firmware complaining it could not load from this device.

After much frustration, I reformatted the bootloader partition to type "Apple_HFS" and tried to bless the ofwboot.xcf file. Blessing should be needed to tell Open Firmware it's okay to boot from that device and file.

I had used the following command on the Mac OS X DVD:
bless --verbose --device /dev/disk0s9 --setBoot

which set the "boot-device" variable in Open Firmware to "pci2/ata-6@D/@1:9,\\:tbxi".
I then rebooted into Open Firmware and changed this variable to "pci2/ata-6@D/@1:9,\ofwboot.xcf", and set the "boot-file" variable to "pci2/ata-6@D/@1:11,/netbsd" to tell Open Firmware where the NetBSD bootloader file and kernel were.

After rebooting the machine, NetBSD "booted". Unfortunately, it immediately kernel panicked in such a way that I cannot easily figure out. It initially repeated "Faulted in DDB; continuing..." a few times, followed by the following:

--db_more--trap: kernel ISI by 0xff847168 (SRR1 0x40003030), lr: 0x1001e4
[1.0000000] Skipping crash dump on recursive panic
[1.0000000] panic: trap
[1.0000000] cpu0: Begin traceback...
[1.0000000] 0x00b8c190: at vpanic+0x144
[1.0000000] 0x00b8c1c0: at panic+0x50
[1.0000000] 0x00b8c210: at trap+0x100
[1.0000000] 0x00b8c2d0: kernel ISI trap by 0xff847168: srr1=0x40003030
[1.0000000]             r1=0xb8c3a0 cr=0x20424238 xer=0 ctr=0
[1.0000000] 0x00b8c3a0: at 0xfffffffc
[1.0000000] 0x00b8c3c0: at OF_read+0xb0
[1.0000000] 0x00b8c3f0: at ofw_stack+0x44
[1.0000000] saved LR(0x2c) is invalid.cpu0: End traceback...

This repeated itself over and over until I hard powered off the machine. By the looks of it, it can't read something in Open Firmware, although I wouldn't know what.

All this being said, it is rather strange behaviour considering I was able to install NetBSD on an iMac G3 DV+ (PowerMac2,2, 450 MHz) recently without issue. Running the initial Open Firmware boot command simply specifying "hd:9" worked flawlessly, and there was no need for me to bless anything.

I understand if I messed up this installation by overcomplicating the partitioning and Open Firmware setup, but I have exercised any troubleshooting method that I can think of. Any advice or suggestions would be much appreciated.

Thank you,
Thomas (they/them)

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