External SCSI Plumbing

[Lucky Leavell [RIS]]

I recently acquired an HP ScanJet IIcx which I have determined should work
with my UW7 box using an Adaptec 1542B. I know I have to remove the
terminator on the 1542B for the external cable but how are external
devices terminated? (I don't have a manual for the ScanJet yet or I might
already know that one?)

One final question: There are two SCSI connectors on the back of the
ScanJet, one looks like the usual 50 pin external connector but the other
looks like a DB-25 female connector; a DB-25 male plugs into it just fine.
What sort of SCSI connector is that? SCSI-1?

I also found sane on the SCO skunkware archive ...)

Thank you,
Lucky

Lucky Leavell Phone: (800) 481-2393 (US/Canada)
UniXpress - Your Source for SCO OR: (812) 366-4066
1560 Zoar Church Road NE FAX: (812) 366-3618
Corydon, IN 47112-7374 Email: lu...@UniXpress.com
WWW Home Page: http://www.UniXpress.com

Thank you,
Lucky

Lucky Leavell Phone: (800) 481-2393 or (812) 366-4066
UniXpress - Your Source for SCO FAX: (888) 231-9640 or (812) 366-3618
1560 Zoar Church Road NE Email: lu...@UniXpress.com
Corydon, IN 47112-7374 WWW Home Page: http://www.UniXpress.com

[Tony Lawrence]

"Lucky Leavell [RIS]" wrote:
>
> I recently acquired an HP ScanJet IIcx which I have determined should work
> with my UW7 box using an Adaptec 1542B. I know I have to remove the
> terminator on the 1542B for the external cable but how are external
> devices terminated? (I don't have a manual for the ScanJet yet or I might
> already know that one?)

External devices usually have two connectors: one to plug
your cable in, the other to either go on to the next device
or stick a terminator on if it is the last. Most scsi
devices come with an appropriate terminator; if not you can
buy them from places like Granite Digital, etc.

--
Tony Lawrence (to...@aplawrence.com)
SCO/Linux articles, help, book reviews, tests,
job listings and more : http://www.pcunix.com

[Bill Vermillion]

In article <Pine.GSO.4.31.0102241249400.29802-100000@shell1>,

Lucky Leavell [RIS] <r...@iglou.com> wrote:

>I recently acquired an HP ScanJet IIcx which I have determined
>should work with my UW7 box using an Adaptec 1542B. I know I have
>to remove the terminator on the 1542B for the external cable but
>how are external devices terminated? (I don't have a manual for the
>ScanJet yet or I might already know that one?)

>One final question: There are two SCSI connectors on the back of
>the ScanJet, one looks like the usual 50 pin external connector but
>the other looks like a DB-25 female connector; a DB-25 male plugs
>into it just fine. What sort of SCSI connector is that? SCSI-1?

The 50 pin connector that looks like an overgrown parallel
Centronics connector is a SCSI-I connector.

25 pin SCSI connectors do exist but the violate the SCSI standard
which among other things calls for one ground wire for each signal
wire.

Apple SCSI from the early McIntosh machines used a 25-pin SCSI
cable. The SCSI connector on the back of the Iomega ZIP drives
is also 25-pin SCSI.

I forget the manufacturer at the moment but in the mid-late 1980s -
this is the early Mac era, there was one other manufacturer who
used the 25 pin cable - and as I recall it was wired differently
so that a power pin was swapped from the 25 pin side to the larger
side and could burn-out/short-out the device or the card.
You only have to worry about that if you are in the habit of buying
old computer 'stuff' at swap-meets and flea markets.

Bill
--
Bill Vermillion - bv @ wjv . com

[Simon Hobson]

On Sun, 25 Feb 2001 0:07:30 +0000, Bill Vermillion wrote
(in message <G9ADo...@wjv.com>):

>> One final question: There are two SCSI connectors on the back of
>> the ScanJet, one looks like the usual 50 pin external connector but
>> the other looks like a DB-25 female connector; a DB-25 male plugs
>> into it just fine. What sort of SCSI connector is that? SCSI-1?
>
> The 50 pin connector that looks like an overgrown parallel
> Centronics connector is a SCSI-I connector.
>
> 25 pin SCSI connectors do exist but the violate the SCSI standard
> which among other things calls for one ground wire for each signal
> wire.
>
> Apple SCSI from the early McIntosh machines used a 25-pin SCSI
> cable. The SCSI connector on the back of the Iomega ZIP drives
> is also 25-pin SCSI.

Well Apple used the 25 pin connector partly due to space constraints, and it
became a de-facto standard. A number of peripheral manufacturers did exactly
what is on this scanner as it means that a customer can use the "system"
cables that come with the devices to daisy chain them together, rather than
going out and buying a "peripheral" cable (I think this the correct
recollection of Apples terminology).

A "System" cable has a 25 pin conenctor at one end and a 50 pin at the other,
a "peripheral" cable has 50 pin connectors both ends. It became normal
practice to supply a system cable with most devices, as that was what most
customers needed. But some manufacturers figured that if a customer bought
two devices, they probably have two system cables - so if they make the
peripheral with a 25pin socket, the customer can use the cables he already
has instead of going out and buying a peripheral cable (which they probably
forgot to buy in the first place).

As a dealer, I found this annoying, but not as annoying as Animas who had a
conpletely non-standard cable used by nobody else !

Simon

[Bill Vermillion]

In article <01HW.B6C986610...@news.demon.co.uk>,

Simon Hobson <si...@no-spam.ccomms.demon.co.uk> wrote:
>On Sun, 25 Feb 2001 0:07:30 +0000, Bill Vermillion wrote
>(in message <G9ADo...@wjv.com>):

>>> One final question: There are two SCSI connectors on the back of
>>> the ScanJet, one looks like the usual 50 pin external connector but
>>> the other looks like a DB-25 female connector; a DB-25 male plugs
>>> into it just fine. What sort of SCSI connector is that? SCSI-1?

>> The 50 pin connector that looks like an overgrown parallel
>> Centronics connector is a SCSI-I connector.

>> 25 pin SCSI connectors do exist but the violate the SCSI standard
>> which among other things calls for one ground wire for each signal
>> wire.

>> Apple SCSI from the early McIntosh machines used a 25-pin SCSI
>> cable. The SCSI connector on the back of the Iomega ZIP drives
>> is also 25-pin SCSI.

>Well Apple used the 25 pin connector partly due to space
>constraints, and it became a de-facto standard.

It was only 'de facto' in the Apple world. The other SCSI
manufacturer - I forget the name - had a cable that had wiring
backwards and if put on an Apple or another non-standard 25 pin
connector - could blow out the adaptor.

> A number of peripheral manufacturers did exactly what is on this
>scanner as it means that a customer can use the "system" cables
>that come with the devices to daisy chain them together, rather
>than going out and buying a "peripheral" cable (I think this the
>correct recollection of Apples terminology).

And SCSI specs call for one ground wire for each signal wire. You
can't do that in the 25-pin world. It is cheaper - but cheaper is
often the worst choice.

>A "System" cable has a 25 pin conenctor at one end and a 50 pin at
>the other, a "peripheral" cable has 50 pin connectors both ends. It
>became normal practice to supply a system cable with most devices,
>as that was what most customers needed. But some manufacturers
>figured that if a customer bought two devices, they probably have
>two system cables - so if they make the peripheral with a 25pin
>socket, the customer can use the cables he already has instead of
>going out and buying a peripheral cable (which they probably forgot
>to buy in the first place).

That may make sense in the Apple world. Didn't work too well in
the server arena where I spent most of my time.

>As a dealer, I found this annoying, but not as annoying as Animas
>who had a conpletely non-standard cable used by nobody else !

Never heard of Animas. All the systems I used - been with Unix
since 1983 - had the big 50 pin centronics for the I - except for
the Zip drive.

I can appreciate your problems as a dealer - with having to stock
more cables than you'd like. In today's world so often the SCSI
cables that are stocked aren't very good to start with. Good SCSI
cables cost money.