Thanks to John Francini, francini_at_progress.com
and "Paul Kitwin (mobile)" <basker_at_ricochet.net>
One last question though...
HOW can I determine whether a cable has the termination or not if it isn't
labeled!?
SUMMARY:
The termination is necessary at the point where you switch from wide to narrow.
Termination is taken care of by some controllers. Basically if it sees a
narrow device on a
wide bus, it drops the entire bus to narrow. If you put a wide device on a
narrow bus, the wide device will act as a narrow. But what I was looking
for was after having a wide device as the first on the chain.
Note well that once you've narrowed the bus, you can't widen it beyond the
narrow device. (Not necessarily true if you get an adapter to pass the
higher byte through the bus, like listed at
http://www.adaptec.com/support/configuration/connect.html)
In other words:
a bus that is arranged:
7 0 1 2 3 4
controller---wide---wide---narrow--narrow--narrow
is OK,
while a bus that is arranged:
controller---wide---wide---narrow---narrow---wide
will end up with the last wide device running in narrow mode (unless you
get the needed adapters)
The high byte termination would be needed between the wide and the narrow
devices in the first example. A high-quality wide-to-narrow SCSI cable (such as
one from DEQ itself) will already have this termination built in.
Thanks!
At 11:14 AM 3/31/99 -0500, I wrote:
>Quick question as I cannot remember correctly.
>
>I know you can put a narrow device on a wide bus.
>And you can put a wide device on a narrow bus.
>Either one utilizing a 50pin to 68pin adapter.
>
>But in which direction is it necessary to have termination of the high byte
>of the bus?
>
>
>--------------------------------------------------------------------------
>Dan Kirkpatrick dkirk_at_phy.syr.edu
>Computer Systems Manager
>Department of Physics
>Syracuse University, Syracuse, NY
>http://www.phy.syr.edu/~dkirk Fax: (315) 443-9103
>--------------------------------------------------------------------------
--------------------------------------------------------------------------
Dan Kirkpatrick dkirk_at_phy.syr.edu
Computer Systems Manager
Department of Physics
Syracuse University, Syracuse, NY
http://www.phy.syr.edu/~dkirk Fax: (315) 443-9103
--------------------------------------------------------------------------
Received on Wed Mar 31 1999 - 16:49:23 NZST