[filmscanners] RE: Which SCSI Card for SS4000

["Thomas Maugham" <TMaugham@yahoo.com>]

Arthur and Austin:

You may well be right but as I said previously, all is working well so I'm
not going to mess with it at this point.  I am keeping the info you sent me
just in case the SCSI Gods decide to punish me and then I'll make
appropriate modifications.

I know about the SCSI problems you describe.  When I retired I was manager
of an IT applications development group for a very large company.  My group
did mostly software but sometimes got involved in hardware when an
application and user needed addditional devices such as scanners, cd
burners, JAZ/ZIP drives, etc.  The PC hardware guys hated to mess with them
as they always had issues with the SCSI cards, cables, and the devices
themselves.  Adding fuel to the fire was that we had two PC manufacturers,
Compaq and Dell, and several different models of each thus no two
installations were ever the same. We had issues with serial and parallel as
well as we often had to connect serial data capture devices and non-standard
types of printing devices which caused many problems too.  One of my guys
used to say that "plug and play" in reality was "plug and pray"!

Thanks very much for your helpful advice.  It's generous and knowledgeable
people like you who make this list as meaningful as it is and I certainly
appreciate it!

Best regards,

Tom

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Arthur Entlich
Sent: Monday, September 09, 2002 11:07 PM
To: TMaugham@yahoo.com
Subject: [filmscanners] Re: Which SCSI Card for SS4000


Actually, I suspect your thinking wasn't correct previously (and it
appears to me your still not set up correctly now). In regard to the
SS4000, this might explain why the 25 pin wasn't working correctly.
Since it was not terminated, in spite of being the last physical device
on that side of the chain, the use of the "less securely grounded"
cabling may have been enough to cause the upset, and the use of the
Centronix 50 M may have "saved the day". Incorrect termination doesn't
always lead to disaster, but it certainly makes it more likely.
Termination stops "echoing" of the signal back down the cable, but good
quality cables may help to prevent this problem by allowing for a strong
enough "correct" signal that the echo doesn't cause enough conflict to
be noticeable.  It may be slowing down the speed if data has to be sent
more than once.

Also, your SCSI card being device 7 has nothing to do with
auto-termination.  Almost all, if not all SCSI cards are device 7. Your
card is actually in the center of the chain (most SCSI cards which have
both internal and external connectors have the internal connection chain
making up one end, and the external chain the other).  If either
connection is not in use, then the card becomes the "end" of that side
and is automatically terminated.

So, in your case, your CD burner is the end of the internal side, and
should be terminated, the card should NOT be terminated (which it seems
in your case it will automatically decide not to do) and the last device
on the external side (the flatbed in this case, previously the SS4000)
should also be terminated.

This is just one of the many reasons SCSI is fast being left behind for
most consumer applications.  The rules are just too easy to
misinterpret.  Apparently SCSI interfacing was one of the most expensive
customer support issues facing companies that used it for consumer
applications and although USB 1, 2, and Firewire have certainly had
their problems (Via chip set for starters), they are much more user
friendly, when the hardware does what it is supposed to, at least.

Art


Thomas Maugham wrote:

> You're correct, of course, and my SCSI card is device 7 (the maximum) thus
> auto termination is working.  My CD burner (internal) is device 2, my
> external JAZ and ZIP drives are 4 and 5 repectively, my SS4000 is 6 and my
> flatbed scanner (last physical device on the chain) is 3 so all is well
(at
> least for now!!!) in SCSI Land!  The termination switch on the SS4000 was
> set to OFF previously and, of course, now it still is. With the exception
of
> the flatbed scanner, all the other devices have been up and running since
> last Christmas and there haven't been any problems.  Adding the flatbed
> scanner was simple and everything else still works.
>
> But just to be safe, at each full moon I sacriface a goat or two to
> hopefully keep the SCSI Gods appeased!
>
> Thanks for the good information, it confirms that my thinking is correct.
>
> Tom
>


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