🚀 go-pugleaf

In article <25065@agate.BERKELEY.EDU> lauac@qal.qal.berkeley.edu (Alexander Lau) writes:
>In article <7598@spool.cs.wisc.edu> engber@shorty.cs.wisc.edu (Mike Engber) writes:
->Has anyone else had problems booting an SE/30 with an external SCSI
->drive attached, but not powered up. This seems like the same problem
->a mac+ with old ROMs has. Did Apple make the same mistake twice?
->(the drive I used was a CMS 40M)
->-ME

>Nah, it's not Apple's fault. All SCSI devices on a chain must be on.
>That includes your external drive, since it's connected.

It's not Apple's fault -- but that's not the reason.  The problem is that the
TERMINATORS need to be powered up in order to run the SCSI bus.  Prior to the
Mac II, terminator power was NOT supplied by the Mac, so that the peripheral
at the end of the chain had to supply its own power.  With the Mac II and
later systems, terminator power is supplied at the SCSI connector, but I have
discovered that many disk controller boards do not have provision for accepting
terminator power from the bus -- hence the device with the terminators must be
powered up.  Intermediate (non terminated) devices do not need to be powered
up for the bus to run.

Marc Kaufman (kaufman@polya.stanford.edu)