On May 29, 2004, at 02:18 am, Doug Anderson wrote:
I picked up an old Apple 40SC external hard drive. The previous owner has replaced the drive with a 1GB drive.
When I connect this unit to my SE/30, the SE/30 will not boot from its own internal HD, I get the flashing system disk with ? symbol in it. If I disconnect the drive and restart, it works fine. With the computer up and running, if I connect the external drive to the SE/30, the SE/30 will lock up. If I unplug the drive the SE/30 becomes responsive again.
The reason is that the termination on the SCSI bus is not right when you attach the drive *or* the ID is conflicting. Generally 4-6 are safe IDs for external units as 1-3 are used for internal units (on a machine with 2 HDDs and a CD-ROM that is). On the SE/30 the HDD in the machine *should* be ID 1. Never use 7 - that is the Mac itself's reserved number.
Try not using a terminator as well - the logic seems a bit backwards but as I remember if you terminate a bus that is already terminated internally (which it will be at the hard disk in any 1 hard disk Mac that is still setup as the factory intended) it causes all sorts of weirdness - I'm pretty convinced this is because the way the system is wired in a 68k Mac the external port is in the stream between the SCSI controller and the internal SCSI on a single bus so terminating the internal drive automatically terminates the end of the bus. I don't know that for sure - it's just a theory related to the fact nearly every 68k machine I have used external SCSI on didn't need a terminator - the only exception is my 840av, because it has no hard disk on the internal SCSI lines (instead it has a 18GB U160 on an ATTO SEIV card). I believe the Quadra 900 and 950 also are exceptions as they are dual SCSI bus machines (unless you are running System 7.1 or earlier).
-- Mark Benson
AIM - SilValleyPirate MSN - [EMAIL PROTECTED] Visit FlatPackMacs online: <http://fpm.68kmac.com> Visit my Homepage: <http://homepage.mac.com/markbenson>
"Never send a human to do a machine's job."
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