On Sat, 3 Feb 1996, Scott L. Burson wrote:

> 
> I figured there was some story like that behind it, but I still think it odd
> because there is nothing whatever in SunOS that treats sd0 specially.  You can

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.  Sun either didn't realize this, or didn't think of the 
implications when they shipped most of their early systems with the
boot drive set as SCSI ID 0.  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.  

To avoid confusion they did the silly remaping in SunOS that we all
know and love.  Note that this applies to the sun4m as well as the
sun4c.