Re: scsi connection

[dempson@actrix.gen.nz (David Empson)]

Dave Althoff Jr <dalloff@gcfn.org> wrote:

> Here's a SCSI termination question for you...
> 
> I have an Apple high-speed SCSI card.  I built for myself a SCSI cable
> which runs from the port on the SCSI card to a DB-25 connector on the back
> of the computer, then to the 50-pin connector on my *internal* hard drive,
> which is mounted in a Vulcan-GS power supply.

This means you've actually got a three-way connection at the DB-25 (to
the SCSI card, to the internal hard drive, and the external connection).

I haven't had a look at the relevant part of the SCSI standard, but I
imagine this sort of arrangement violates the standard.  It may depend
on the length of the cables going from the connector to the SCSI card
(pretty short) and the internal hard drive.

I'd be inclined to treat this as if the SCSI card was in the middle of
the chain rather than at the end (the Vulcan is at the end).  Strictly
speaking, you should remove the termination from the Apple HS SCSI card,
have the internal hard drive terminated, and also terminate the last
external device (the Zip drive).

You can often get away with slightly incorrect termination, particularly
with short cables going to internal devices.  I'd agree with Wayne's
reply - if it ain't broke, don't fix it.

> It's been a while since I set it up, and it works great...but what is the
> appropriate location for the SCSI terminator in this sort of set-up?  I
> believe I have termination on the internal drive.  Would it make any
> difference if I had more devices hanging off of the ZIP?

If you were going to add another external device, I'd definitely
recommend eliminating one of the internal terminators, and adding
termination after the last external device.