Cannot boot installer on PowerBook6,8

[Julio Merino <julio%meroh.net@localhost>]

Hello!

I've just got a PowerBook6,8 (the last G4 model, with 768MB of RAM)
and am trying to install NetBSD on it. Unfortunately... I haven't even
been able to even boot the installer yet :-( I knew this was going to
be difficult based on past experience with a Mac Mini, but this one
seems much harder...

Here is what I get:

>> NetBSD/macppc OpenFirmware Boot, Revision 1.12 (Wed Nov 29 04:07:01 UTC 2017)
6068324+127544=0x5e8e60
 start=0x100000

Decrementer exception at  %SRR0: 00000000  %SRR1: 00083030
 ok
0 >

I've tried infinite combinations of: different partition schemes (MBR,
APT), different file systems (MSDOS, UFS, HFS, HFS+), different
versions of ofwboot (xcf/elf, and -current/5.0/5.2 because the one in
5.0 is what worked for my old Mini) and even different media (mostly
from a USB stick, but also tried copying the loader and the
installation kernel to the existing HFS+ partition for Mac OS X). None
have worked, though sometimes the error changes to "invalid memory
access".

Looking online, I have found various threads reporting similar problems:

http://mail-index.netbsd.org/port-macppc/2006/02/10/0000.html
http://mail-index.netbsd.org/port-macppc/2008/06/05/msg000238.html

... but no solution.

Any new hints?

Thanks

-- 
Julio Merino -- http://julio.meroh.net/