Technical Q&A HW96

Open Firmware version number

Q: The Open Firmware version number displayed when I enter the user interface seems to change with version numbers that do not increase with time. Can you explain this fact?

A: Yes, I'm assuming the "version" to which you refer is from the Open Firmware device tree/openprom node model property. Given that, the IEEE 1275 Section 3.5 "Standard System Nodes" defines this node as one having a node property called "model." Annex A.2 "Specification" defines the model property as one which is a "manufacturer-dependent" string. The string format "is arbitrary." Therefore you may not assume a version number as one that will increase as a function of time. The version number is meant to be used by the Apple Open Firmware group. The numbers are unique and possess meaning for their version control.

Here is a code example of a version number that is displayed when you enter the Open Firmware user interface, and that same version number (called a model property) in ther device tree. Note that your number most likely will be different.

Apple PowerMac1,1 1.1f4 BootROM built on 04/09/99 at 13:57:32
Copyright 1994-1999 Apple Computer, Inc.
All Rights Reserved.
OpenFirmware 3.1.1  <-----------here is the version number
To continue booting, type "mac-boot" and press return.
To shut down, type "shut-down" and press return.
 ok
0 > dev /openprom  ok  <--------this is how to get to the openprom node
0 > .properties  <--------------this is how to display the properties
name                    openprom
device_type             BootROM
model                   OpenFirmware 3.1.1  <------and the version number
relative-addressing
supports-bootinfo

In summary, the version number is a 1-to-1 transformation from the model property. It is unique. Therefore, version numbers are not a linear function of time in canonical form, y=mx+b. They are random, but unique.