Target Disk Mode
I found a G4 Mac Mini on Craigslist, intent upon experimenting with MorphOS. It arrived packed well, but the hard drive was dead. I cracked it open, and swapped the drive, but no joy. I tried another drive, and even from the option-boot screen, the Mini didn’t see the drive.
I booted from several install discs, and none worked. In a fit of masochism, I even booted into Open Firmware, but couldn’t get that to work either. I plugged a USB IDE drive sled into my Mac Pro, and restored the Tiger DVD to it…. nope. Mini couldn’t see it.