According to ADC documentation:
You can access Open Firmware this by holding down Command-Option-O-F at boot time.
However, in reality this does not work on current hardware. Does anybody know if there is a way (through trigger-keys, etc.) to get to an EFI console on contemporary-architecture (i.e., Intel) Macs?
EDIT: I am attempting to set up (and document) various Kernel Debug environments.
In experimenting with the boot-loading mechanisms of OS X, I have come to the following conclusion:
There are at least 3 different architectures:
Open Firmware (PowerPC hardware)
EFI, in which rEFIt works properly
a transitional(?) EFI [32bit?] which is used on early Intel machines, where rEFIt does not work
I had posted this question after encountering this 3rd case, which seems to occur on Core Duo (not Core 2 Duo!) machines: the result being that, once rEFIt is installed, the rEFIt menu DOES correctly get displayed at boot time, however is unusable because it receives no keyboard or mouse input (no USB drivers loaded?) and ultimately always ends up booting into the highest numbered boot partition.
Therefore, in scouring ADC documents and looking for a means to drop into a firmware/EFI console at boot-time, I came across the (somewhat outdated) statement from ADC [see above] and thought that it might be useful to ask on SO if anyone knew of an alternative.
Answer
Only Macs with PowerPC architecture have Open Firmware. The newer Intel based macs have EFI. As these firmwares are completely different their functionality is not equal.
AFAIK EFI does not have the corresponding feature of Open Firmware Access.