[882] in linux-scsi channel archive
Re
daemon@ATHENA.MIT.EDU (Hartmut Niemann)
Wed Nov 6 04:12:57 1996
From: Hartmut Niemann <niemann@cip.e-technik.uni-erlangen.de>
To: rberry@albany.net (Russell Berry)
Date: Tue, 5 Nov 1996 16:47:03 +0100 (MEZ)
Cc: linux-scsi@vger.rutgers.edu (Linux SCSI)
In-Reply-To: <327ECCF5.16C2AB32@albany.net> from "Russell Berry" at Nov 5, 96 00:13:25 am
> I hate to sound like an idiot here, because I'm not..
>
> no, really, I'm not! I work with this crap every day, my mind
> just seems to be drawing a blank right now. I have:
> NCR53C810-----1G_fast_scsi-II terminated scsi-id0
> |------1G_fast_scsi-II not-terminated id1
> |------.5G_fast_scsi-II terminated id2
>
>
> all three disks internal, nothing external (yet) they work,
> and seem fast, I'm just unsure at this particular moment if
> I should have two of them terminated or not...
>
> conformation anyone...
>
>
> ---russ
>
AFAIK: no termination in id0, but termination on the NCR is
recommended if the NCR is the last on the cable.
Fast SCSI requests active termination. (Confirmation please?)
From my understanding of high frequency electronics, this
is due to the fact that fast devices have a shorter signal rise
time, which leads to a higher signal bandwidth and problems
with signal reflection with improper termination. This would
require active termination as soon as one drive is Fast,
no matter how fast the bus is driven (even if used asynchronously).
If the NCR only offers passive termination, you probably could put
it in the middle, if space and cable length permit:
|---1G_fast_scsi-II terminated scsi-id0
|-----NCR53C810- not terminated-
|------1G_fast_scsi-II not-terminated id1
|------.5G_fast_scsi-II terminated id2
(Any comments?)
+--+
!cu!
+--+ Hartmut
--
Hartmut Niemann
niemann@cip.e-technik.uni-erlangen.de
Zum Aussichtsturm 18 D-91080 Marloffstein
