I'm at work so I can't get a live one off of my system, but I found  
this with some google-foo:


nvramrc
      hex
      : $D find-device ;
      : $E device-end ;
      : $L BLpatch ; : $R BRpatch ;
      : $X execute ;
      : $p 0 to my-self property ;
      : $a " /chosen" $D $p $E ;
      10 buffer: km
      dev kbd
      get-key-map km swap move
      $E
      : ck 0 do swap dup 3 >> km + c@ 1 rot 7 and << and or loop ;
      : bootr 0d word count encode-string " machargs" $a
      8 0 1 ck if 0 and else f 29 3d 0 3 ck if 40 or then then
      if bye else cr 20 0 do ['] boot catch drop 500 ms loop then ;
      dev enet
      ' open constant $M
      : $M2 $M 710 - $X ;
      : rl@ -7D9D40 $X ;
      : chstat begin $M2 $M 14f8 - $X -7D6C20 $X rl@ 400 and 0= until ;
      : bmstat begin $M2 $M 13F0 - $X rl@ 100 and until ;
      : xmt1 get-msecs $M 720 - ! chstat $M A00 - $X bmstat chstat ;
      ' xmt1 ' WRITE 10 + l!
      62 ' READ 7 - c!
      : READ { _p _n ; _a } begin _p _n bead -> _a _a 2+
      if _p c@ 80 and 0= else 1 then until _a ;
      $E
      dev /packages/obp-tftp
      : $M over + ['] noop $L ;
      ' open E8 $M EC $M F0 $M F4 $M F8 + ' true $L
      $E
      dev /packages/mac-parts
      : $M -7E89E0 $X 8000 alloc-mem 4 -7E89E0 $X ;
      ' load 268 - ' $M $L
      $E
      dev ide0
      f3000038 constant $hfr
      : $M $hfr rl@ or $hfr rl! 10 ms ;
      : ata-enable 4 $M 80 $M 800000 $M 100 $M 20 $M 40 $M ;
      : $M2 use-ata-interface ata-enable true ;
      : set-device-ID set-drive-select ;
      : reset-atapi-bus reset-ata-bus ;
      ' open ' $M2 $R
      ' enable-bus ' ata-enable $R
      ' reset-ata-bus 2c + ' 2 $L
      $E
      dev ide1
      f3000038 constant $hfr
      : $M $hfr rl@ or $hfr rl! 10 ms ;
      : ata-enable 4 $M 80 $M 800000 $M 100 $M 20 $M 40 $M ;
      : $M2 use-ata-interface ata-enable true ;
      : set-device-ID set-drive-select ;
      : reset-atapi-bus reset-ata-bus ;
      ' open ' $M2 $R
      ' enable-bus ' ata-enable $R
      ' reset-ata-bus 2c + ' 2 $L
      $E
      dev scsi
      : $M ['] do-cmd + ;
      : $M2 5 us -5f0 $M $X ;
      : $M3 -710 $M f over $X $X ;
      -1AC $M ' $M2 $L
      100 $M ' $M3 $L
      1 124 $M !
      $E
      unselect-dev


You will probably have to roll your own pure ISO instead of a hybrid  
to get it to boot on an old world mac as well.

http://mail-index.netbsd.org/port-macppc/2005/11/18/0001.html



On Jul 18, 2006, at 10:48 AM, A. P. Kennedy wrote:

> Hi,
>
> I need a little help. My wife brought home a Power Macintosh (Beige)
> G3 Desktop 233 Mhz. I appears to be an early version. It has
> openfirmware verson 2.0f1. Yes, I got into the openfirware prompt
> without any problems. I have no operating system or OS CD, and the
> harddisk did not contain a functional OS. I can't boot NetBSD. I have
> been reading the netbsd installation instructions, and found that I
> must install nvram patches without Mac OS to get this system to boot,
> using nvedit.
>
> I don't have access to any Mac bootable install CD's. However
> I was reading a section in the faq for macppc that said the
> following:
>
> **** Start ****
>
> Once you've got the 0 > Open Firmware prompt on your screen or
> serial console, you can try installing NetBSD starting at the
> "Getting to the Open Firmware Prompt (Without using Mac OS)"
> section in the INSTALL notes. If your system can't boot NetBSD,
> then post to port-macppc@NetBSD.org asking someone to mail you
> the nvram patches for your model. You can use your serial
> console to paste the nvram patches into Open Firmware. See the
> NetBSD/macppc nvedit HOW-TO for help with this step. Once you do
> this, you should be golden.
>
> **** End ****
>
> So can someone please mail me the nvram patches for a
> Apple PowerMacintosh G3 (Beige G3, Revision 1, Open Firmware
> 2.0f1) please?
>
> Trying to be golden.
>
> Thanks,
>
> Alan
>
>
> !DSPAM:44bd052b36711060613879!
>
>
>