Try turning off your modem (or other device attached to the modem port).
Open Firmware will try to communicate with the serial port, and the
modem will echo OF's text, confusing OF.
 
On non-7200s, you can tell OF to send its I/O to the screen and
keyboard,
which avoids this problem. It's in the FAQ on cap.anu, I think.
(Eventually, it should end up in this FAQ. Until then, see the List
Of FAQs in the top category.)
 
jonh@cs.dartmouth.edu
-----------------------------
If that don't work, and also cmd-ctrl-power doesn't reboot the machine,
there is a cure, but it's rather extreme. You can remove your machine's
internal battery and unplug the power cord for about half hour. Use this
as
the VERY LAST RESORT!!! There are too many dangers involved to mention
here.
j-eo@students.uiuc.edu
-----------------------------
Before you try that, try just rebooting/power cycling, and try
holding cmd-opt-R-P during the chime and for a few seconds after. The
fix I
mention above was for when your system won't switch over to linux, not
so much for when it won't switch back to MacOS...
 
jonh@cs.dartmouth.edu
 
-----------------------------
Here's a checklist to go over in case you have this symptom:
 
- Make sure the device on the modem port is off; Open Firmware talks
  to the modem port, and some modems stop OF from booting (my USR
  33.4 does not).
 
- MAKE SURE YOU DOWNLOADED AND UNCOMPRESSED IN BINARY.  This has
  bitten me a few times, and has even been the embarrasing solution
  to queries I've made to the list.
 
- Make sure you have the latest quik.  Quik is the new version
  of milo (on the UNIX end).  Paul has recently updated the MacOS
  version.  Once you have downloaded and installed the rpm, run
  quik (quik -vf) to install the right bits of first.b and second.b
  in the boot clock of the root partition.  If you do this from MacOS,
  the right bits will be written, but your /etc/fstab will be
  regenerated.
 
- Check to make sure your machine is supported.  See the list of
   supported machines in the FAQ-O-MATIC.
 
-----------------------------
 
I have seen a bug now 5 times on 5 different machines where it is
impossible to zap the PRAM after a bad configuration in OF giving
a black screen after restart. It becomes impossible to boot the
Mac with MacOS or Linux and the screen stays definitely blank.
The only solution is to open the Mac to remove the battery BUT :
 
In all cases, people have an additional ADB device (joystick,
touchpad...).
 
Removing the additional ADB device from the ADB bus solves the problem
without opening the Mac and removing the battery...
 
After removing the ADB device and restarting the Mac, command-option-P-R
works as expected...
 
 Serge.Rossi@renault.fr
 
-----------------------------
 
In even worse cases, the Command-Option-P-R key sequence won't work.
A few things to check:
   1. Make sure the Caps-Lock key is not down.
   2. Try an older Keyboard with a mechanical Caps-Lock (seems that 
      in some cases the soft Caps-Lock on the AppleDesign Keyboards 
      causes some problems with a Wigged out OF/PRAM/nvram.
   3. Try the above battery removal, say, 15 minutes or so.
   4. If that doesn't work (as was the case with my Performa 6400) 
      there's a button on the Motherboard that appearently resets 
      the PRAM and nvRam. I tried this a number of times by just
      clicking it, but I finally held it down for 20+ seconds, and 
      was finally able to have my machine back w/o sending it in for 
      repair, all the while avoiding trying to explain to the Support 
      Personel why I was mucking with OF :)
 
Hope this is some help to those who encounter the extreme
frustration I had with trying to make my machine live
again.
 
Timothy Jones  fstaj@aurora.alaska.edu
 

Turning off the modem may be a problem, especially if you're running a fax
server and need to reboot remotely.
The solution is to turn off echo on the modem:

ATE0&W

That'll turn off echo and save it to the modem's NVRAM.
This works fine on my 7200, OF no longer gets confused on boot.