[NTLUG:Discuss] SCSI problems - (Was: aic7xxx: infinite...)

[Kevin Brannen]

Steve Baker wrote:
> 
> Kevin Brannen wrote:
> 
> > SCSI problems are generally attributible to 3 things:
> > 1. ID settings.
> > 2. Termination.
> > 3. Cables.
> >
> 
> Hmmm - this is an appropriate time (for me) to discuss SCSI.
> 
> I've been wrestling with a new CD-writer.
> 
> I have been using an adaptec AHA152x to drive my scanner for over
> a year now - with no problems.  I was given the chance to buy a
> completely unused (if a little old) HP6020 CD writer (it's the
> same device as the Philips 2600) - since I had a spare port on
> the SCSI card, I jumped at the chance.
> 
...

Eeek!  You're really having a bad day here. :-)

> 
> >From the list of suggestions for typical sources of SCSI
> problems:
> 
> ID SETTINGS:
> 
>   It's ID is 4 - the scanner *was* 6 - but that's disconnected
>   now "just to be sure".

In theory, it really shouldn't matter.  However, when I added my
Yamaha CDRW, I did have problems too.  The Yamaha folks said that
their device liked ID 3 or 5 better than the others (preferablly 3). 
The support guy didn't know why, but that was what the engineers had
told him.  So I moved my tape from 3 to 6, and the CDRW from 4 to 3
and all has been well since.  I know that sounds like voodoo, and I
consider it to be so, but maybe yours has a similiar preference.  Try
perusing the HP web site and see if you can turn anything up.

> 
> TERMINATION:
> 
>   I wasn't quite sure what was the right thing to do.  The
>   Adaptec card has an internal ribbon connector (which
>   is what the CD-writer is plugged into) and an external
>   connector (which is what I was using for the scanner).
>   Right now, both the scanner (when plugged in) *and* the
>   CD-writer have termination - which I imagine is the right
>   thing - and since the scanner still works OK - and
>   the CD-writer works for reading - I can't believe it's that.
>   In case it was intermittant, I read an entire CD onto my
>   hard drive - then re-read the same CD with a normal CD-ROM
>   drive on my son's computer and diff'ed the two - no errors.

Yes, if using internal & external, each must have termination.  Also,
be sure your card is set to NOT terminate either.  I don't know about
the 1520 series, but I used to have a 1542C that had that option on
the card.

> 
> CABLES:
> 
>   Well, the CD-writer has a vanilla grey ribbon cable -
>   about a foot long...what could be wrong with that?
>   The scanner cable is a shielded bundle about 3 feet
>   long - and came with the scanner. This could be
>   problematic I suppose - but it's disconnected right now.

I've found that either they're made well or they're not; and if not,
then you get intermittent problems.  I had one that worked with 2
devices but not 3; hence, there must have been bad connectors.  The
only way I know to troubleshoot this is to have others you can swap in
and test (but that gets a bit expensive).

> 
> > I really like SCSI devices, they generally aren't that hard to get
> > working most of the time.
> 
> Grrrrrrr  :-(

OK, I was thinking of adding HDs when I wrote that.  No master/slave
thing.  Also, I've never had "vendor incompatabilities" with SCSI like
with IDE.  And the limit of devices per controller is a higher too.
:-)

I've also seen a few controllers that are "almost SCSI", though I
suspect that's probably not your problem.  However, my 1542C is just
sitting on the shelf.  I'll offer it to you for testing purposes if
you'd like (I will want it back. :-)  Email me if you want to do that.

Kevin