Note- I've updated the patch slightly based on some research... the Sawtooth 8.6 only seems to like 7400 and 7410 processor models. Reading some opensource PPC code online lead me to believe some 7410s might be a little different then other 74xxs, and the closest match to my 7455 (a ver 3) seems to be a 7410 1.01 (see
http://www.opensource.apple.com/source/xnu/xnu-344/osfmk/ppc/start.s ). OS 9.04 additionally seems to boot with the 7450's, where as 8.6 doesn't. Additionally, as a side note, if "Enable Processor Cycling" is checked in Energy Saver, the mouse pointer freezes when the machine goes "idle". Thus far I have been unable to get the machine to wake from sleep, regardless of the cpu-version, and various settings of CPU Director 2.01 and the latest (paid) XLR8 software, with and without energy saver installed, blah blah...
#define PROCESSOR_VERSION_7400 0x000C....
#define PROCESSOR_VERSION_7410 0x800C....
#define PROCESSOR_VERSION_7450 0x8000....
#define PROCESSOR_VERSION_7455 0x8001....
For all you ever wanted to know about "nvramrc"...
http://www.softpanorama.org/Solaris/Startup_and_shutdown/OpenBoot/nvedit_line_editor.shtml
esentially, get into "open firmware" [command/apple][option][O][F]
to reset to defaults first (if you've screwed something up...) reset-nvram [return] and set-defaults [return], then
nvedit [return] to create a script. this is a little hard to work with, the up and down arrow keys move around in the buffer, [ctrl][L] shows you the script, see the above link. then type
dev /cpus/@0 000c1101 encode-int " cpu-version" property device-end [return]
dev mac-io/ata-4 0 0 " lba-48" property device-end [return]
[ctrl][C] (to exit the editor)
nvstore [return] (to save it)
setenv use-nvramrc? true [return] (to activate it.)
reset-all [return] (to reboot and go!)
I'm _really_ concerned about getting the sleep to work... I've stripped the sawtooth down to just the video card it came with (AGP ATI Rage). It goes to sleep, but when I click the mouse or keyboard and it wakes up, I get nothing- Black screen, optical mouse doesn't illuminate... bummer.