Subject: Re: se/30
To: None <>
From: Kevin Wilson 315-456-1404 <>
List: macbsd-general
Date: 11/07/1994 11:09:26
>    Date: Sun, 6 Nov 1994 21:27:08 -0600
>    From: (mike j. laporte)
>    I borrowed a se/30 from work and took my newly(finnally?) formatted
>    540 drive and hooked it up and it worked fine..(5 megs ram)..booted quick
>    and ran dt without a problem.

Date: Mon, 7 Nov 1994 09:01:44 -0500
From: Ken Nakata <>

> Just worth my $.02, are you sure that your SCSI bus termination is ok
> on the IIci (or else... sorry I don't remember)?  Too many or too few
> SCSI bus terminaters actually do harm, especially when there are
> SCSI-2 FAST drives connected (the system *may* work with slower SCSI-1
> drives).  It sounds like it doesn't work when you have several drives
> connected to your SCSI bus, and it works when the 540Meg is the only
> device except for the Mac on your SCSI bus (correct me if I'm wrong).
> Just in case you don't know how to terminate a SCSI bus properly
> (please don't get offended; I just want to save some net bandwidth),
> you have to have exactly the two drives at the both ends of the SCSI
> chain terminated.  The internal drive should always be and usually is
> terminated as it always is at an end of the SCSI chain.
(Sorry, but for those that don't know about the termination this note
seemed to stop short.)

To know for sure how many terminators you have in your SCSI chain, you
may have to check all your documentation on the drives or even open 
the desk top case (DON'T OPEN THE DRIVE IT SELF!)  What you want to look
for is a set of sockets (usally) near the ribbon cable that attaches
the drive to the SCSI bus internally to the box.  These sockets may be
a collection of 2 DIPs or 3 SIPs and frequently labeled T1 T2 (T3)
(This is what I've typically seen on the dozen or so drive types I've
looked at.) and should be empty on all drives with the possible exception
of the two drives at the ends of the SCSI bus.  If any of the sockets
on any intermediate drive have resistor packs (terminators) in them then
they need to be removed.  Check also for switchs on the outside of the
box that may be labeled TERM (on / off) these should be set to off for
intermediat drives.  Or look for labeling on the case that says External
Termination Required.  (Of course if your drive came from a garage shop
the TERM switch may not be hocked up, or labeling could be inaccurat.)
Having done this you may want to label any unterminated drives as such
on the box (It may save you time in the future.)  Finally if there are no
internal terminators on the last drive in the chain then you will need
an external terminator.  And here too there could be an issue as to
whether the drive connector is suppling power for the terminator.  Check
your manuals.  Finally if an intermediat drive has the internal terminators
and the end drive doesn't, see if you can easly move the drive with the
terminators to the end of the physical SCSI chain.  (Drive ID has no
bearing on where in the chain the drive resides.)

Sorry, what was supposed to be a quick note to check the drive's controller
board turned into a disertation on SCSI termination.  In any event
I hope this helps someone.