When you start Open Firmware on a PowerMac 5500 the integrated monitor is not
enabled so you can't see it.  The problem also exists in LinuxPPC, and
equivalent patches to the kernel fix it.

                                                                Frank Crawford

This procedure was sent to me Adam Brooks:

You wanted to know the "cpoke" commands I used to brighten the display?  
Just type these commands exactly as shown (with a return at the end of 
each line) at the OF prompt Here they are:

cpoke 0a7 0f3000032
cpoke 093 0f3000033
cpoke 03e 0f300003a

BIG thanks to Jens Ch. Restemeier 'jchrr@post.uni-bielefeld.de' for the 
great help.  Those commands should get you a good looking OF interface. 
(so you can give your eyes a rest!!)

I've been doing a little work on my 5500, but haven't had much success.  
See my next post for more info on what's been going on.

Adam Brooks

To set your monitor to always turn on when you boot to Open Firmware:

Reboot.
Cmd-Option-O-F during the chimes
(Where <CR> is return and you DO NOT type quotes.)

Enter `nvedit <CR>', hit <Ctrl-N> a few times and type:
cpoke 0a7 0f3000032<CR>
cpoke 093 0f3000033<CR>
cpoke 03e 0f300003a<CR>
<Ctrl-C>
nvstore<CR>
setenv use-nvramrc? true<CR>

Upon future reboots, the code to turn on your monitor will get run
automatically.

-- COlin Dellow

If you are a Debian user installing Linux onto the 5500 (or 6500, I think)
you must open the System file on your hfs-boot-floppy disk with ResEdit

Find the CMDL resource and add

 video=atyfb:vmode:13,cmode:16

to it.  This disk will now boot properly.   Huzzah!

--Colin Dellow