i'm not detailing the installation process of openbsd on an apple tibook, but the install involved the MBR method, using the entire harddrive.

on the first reboot however, the tibook couldn't boot, it was the old skool mac folder/question mark flashing back and forth.  i suspected that it was an OpenFirmware boot issue, so i focused my efforts in that arena.

in order to boot, i power down the system, and rebooted pressing command-option-O-F to get the OpenFirmware prompt. at the prompt i typed in boot hd:,ofwboot which boots the system correctly.

in order to see what the default boot instructions for the system, get into the OpenFirmware prompt, and type  printenv to see what the default value is. in my case the default for boot-command was set to mac-boot. once you've copied the ofwboot file from the /dos partition (created during the MBR full disk instal) to the root partition, set the environment by typing the following in the OpenFirmware prompt setenv boot-command boot hd:,ofwboot

there it is.