>Actually,  the story I heard is more or less as follows.  The way the 
>SCSI bus works, the higher the device number, the higher the priority
>on the bus.

This is true but not generally important...

>When the sun4c came out they decided to change this practice and set
>the boot drive to SCSI ID 3, one assumes to improve performance.

The *real* story (as if I would know :-) ) is that Sun thought that
people would take their old sun3 shoebox drives and hook them up to
their spiffy new sun4c boxes.  (Perhaps people actually did this with
some of the early sun4 boxes.)  Sun3 shoebox drives were target 0,
so this would fail if the internal drive was also target 0.  The tapes
in shoeboxes were target 4, so target 3 was the `most likely unused'
number below the first tape.

(If Sun were really using IDs for priority, they should have put the
internal drive at target 6...)

Chris