Changing the Open Firmware screen resolution?

Jim Harris jimrh at
Sun Feb 5 14:33:59 EST 2012

From: Jackoverfull [mailto:jackoverfull at] 
Sent: Saturday, February 04, 2012 7:14 AM
To: Jim Harris
Cc: yaboot-users at
Subject: Re: Enable multiple OSX boot option and intellegent labels?

Il giorno 04/feb/2012, alle ore 06.50, Jim Harris ha scritto:

What you wrote was VERY odd, so I must did a few tests on my iMac G3, the results were rather surprising. My compliments: you just led to the discovery of a "new" Tiger bug (or "feature", perhaps).

If I set the resolution on my 10.4.11 system to 640x480 it comes back to the one that was setted previously (1024x768 or 800x600) on logout (shutdown/reboot included), hence setting the open firmware resolution to that one as well. On Mac OS 9 everything works as expected and if I shut down the system with a resolution of 640x480 it boots with an open firmware with big text.

I think, after a few minutes of reflection, this is actually not a bug, but a perverse feature of OS X: actually if you change the resolution to 640x480 from the Preference Pane (not from the menu) you are warned that some software may appear incorrectly (basically because many applications assume a minimum screen estate of 800x600 or even 1024x768). It is possible that someone in apple chose to restore the previously used resolution on a 640x480 logout thinking that noone would ever willingly use a resolution so low.

Anyway, 800x600 could still be a viable choice, see if it fits your needs.

Also, the ASCII art thing wasn't (solely) a joke: it could be a viable way.

>>Jim =============================================
Re:  Encoding.
I am trying to deliberately send all messages to this group in plain-text, so that there are no mistakes.

Re:  Bug (feature!) in Tiger.

This is not a *Tiger* issue.
What I want to do is to set the screen resolution while within *OPEN FIRMWARE* so that the screen is easier to read.

 What I am doing is this:

1.  Perform the Macintosh "four-finger-salute". . .  OPT - CMD - O - F . . . . to get into the Open Firmware editor.
(This is a very bad pun on Microsoft's "three-finger-salute"  CTL - ALT - DEL)

2.  Notice that the size of the displayed characters on the screen is very small.

3.  Execute a "printenv" command to print the entire list of environment variables.

4.  Notice that "screen-#columns" is set to "100"

5.  Notice that "screen-#rows" is set to 40

6.  Set "setenv screen-#columns 50"  and  "setenv screen-#rows 20"  (essentially dividing both numbers in half)

7.  Re-run the "printenv" and note that the values entered have "taken"  also note that the screen-resolution has not changed.

8.  Execute "shut-down" to write novram and power down the computer.

9.  Restart as in #1 above.

10.  Note two things:
   a.  The screen resolution within Open Firmware has not changed.
   b.  Executing a "printenv" shows that the values entered are still there.

I have not figured out a way to make the OPEN FIRMWARE screen text larger.

Any ideas?

p.s.  Ascii art would be both time-consuming and complicated to implement - especially within the confines of the ofboot.b file - to the point where it would be cheaper and easier to just go buy a monitor that is 2 x 1.125 meters in size!  (laughing)

Jim (JR)
<<Jim ============================================

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