Technical Q&A

HW 56 - Determining Open Firmware configuration variables (29-Mar-99)

Q: How do I determine the Open Firmware configuration variables on my machine?

A: First, you must understand that configuration variables are defined by IEEE 1275. For details, look at Section 3.3.1 Configuration variables. Also, the various bindings to the Standard define binding dependent variables by name. You can view these configuration variables at the Open Firmware user interface.

Use the printenv word to display the three-column output. (Not all Macintoshes display these variables using the same format.) The first column is name, the second column is the current value, and the third column is the default value. To reset the variables to factory settings (default), start the Macintosh using the COMMAND-OPTION-P-R keys and wait for the second boot beep before releasing the keys.