@tubetime yeah so external drives used to ship with all the little jumpers off (ID=0) and if you plugged that into your Sun4 it wouldn't boot and then you'd call the service department ... so they wanted to make the main disk some other ID but everyone assumes the boot volume is sd0 ... so some evil genius came up with this plan.

The *good* external drives had a little pushbutton wheel thingy on the back to change their ID :-)