WARNING: You should print this file first and keep it in a safe place. You may need it in case of an emergency.
Boot Variables is a program to adjust the Open Firmware (OF) boot variables stored in non-volatile (battery-powered) RAM on your Macintosh computer. Fiddling with these values is not to be taken lightly; you can very easily render your computer temporarily unbootable by adjusting parameters in this program to have values OF does not expect.
For an introductory explanation of the variables you can adjust in this program, see Apple Technote 1061: Fundamentals of Open Firmware, Part I: The User Interface.
Running Boot Variables
======================
When you start Boot Variables, you are given a simple dialog box with the following dialog items. The values in the item settings are determined by the current values in non-volatile RAM.
• auto-boot Checkbox
This checkbox is used to determine whether OF should let the machine automatically boot using the OF variables settings. Usually, you'll want this to be on. If it's off, you'll need a means of sending commands directly to OF.
• boot-device Popup Menu
This menu is used for selecting the boot device to which OF should pass control. You select or enter the device name you ontained from Milo. Future versions of this program should do some sort of auto-detect of bootable volumes.
• boot-file Editable TextField
This field is important if you have an internal and external scsi bus.
• All Variables Checkbox
Clicking this box expands the dialog to show you the rest of the OF boot variables. Usually, you won't need to mess with these.
• Write&reboot Button
Selecting this button will write the values to non-volatile RAM and reboot the machine. WARNING: Any programs that are open are not automatically closed, so any unsaved changes to open documents will be lost. Use this button with extreme caution.
• Cancel Button
Selecting this button closes the dialog box without affecting non-volatile RAM.
• Write Button
Selecting this button writes the values to non-volatile RAM. Changes will not take effect until restart.
Creating Boot Config Files
==========================
Beginning with version 1.2, you can create boot configuration files to store the boot variable values you can adjust in this program. Just select Save under the File menu, and you will be given a standard Macintosh Save Dialog. You can also open configuration files that you have saved or otherwise obtained.
When your first Boot Variables, you should save the settings under a file called something like "Default Config". This way, you can open this file from Boot Variables and write the settings to non-volatile RAM in case you accidentally write bogus values.
If you open a Boot Variables configuration file from the desktop and hold the option key down while the file is loading, Boot Variables will automatically configure non-volatile RAM and reboot. In effect, this gives you linux in a double-click. WARNING: Any programs that are open are not automatically closed, so any unsaved changes to open documents will be lost. Use this option with extreme caution.
If you run into trouble
=======================
You may have done something you didn't think you did. You may not have the right kind of computer, or maybe it's just that the universe happens to be conspiring against you this day. Whatever the case, you may find yourself the unhappy guardian of an unbootable Mac :( Likely symptoms are a dark screen and no disk activity after a reboot. In this event, you should try to reset the Parameter RAM (PRAM) by doing a soft reset (command-control-power); while the first chord sounds, hold down the command, option, R and P keys simultaneously. Your machine should then start to reboot under MacOS with all the default settings.
If this fails, you may have to remove and then replace the internal battery to zap any values command-option-r-p didn't get. (I've never had to do this, though I've heard others have had to.)
Information
===========
Boot Variables was first written by Paul Mackerras <Paul.Mackerras@cs.anu.edu.au>. Mike Tesch <matesch@students.wisc.edu> then chimed in with Macintosh file and AppleEvent support. Fred Dushin <fadushin@top.cis.syr.edu> revamped the gui, implementing the user interface elements in TransSkel++, a C++ application skeleton based on Paul Dubois' TransSkel C application skeleton.
The current version of the Boot Variables program is available via anonymous ftp at the following location:
ftp://top.cis.syr.edu/users/bootvars/fadushin
Look for the file bootvars.sit.hqx. The file will be a binhexed stuffit archive containing the Boot Variables program and this README.
You can also obtain the sources for this program at the same location. A binhexed stuffit archive contains the above files, plus the source code, a CodeWarrior project, and the latest versions of the TransSkel and TransSkel++ libraries. You may want to obtain the full distributions of these packages before doing any serious development, however.
Version History
===============
8 February 1998
Cosmetic changes: reorganized dialog to fit in a 640x480 display <atong@uiuc.edu>
2 February 1997
Spliced Paul's changes to support PowerBase.
16 January 1997
Inherited code from Paul and Mike. Removed GUI code from Paul's bootvars.c and implemented a GUI in TransSkel++ application skeleton. Incorporated Mike's Apple Event handlers and config files.
