[H-GEN] SCSI Termination

Hilton Travis QuarkComputers at email.com
Sun Jun 4 00:32:56 EDT 2000

[ Humbug *General* list - semi-serious discussions about Humbug and ]
[ Unix-related topics.  Please observe the list's charter.          ]

Hi Chris,

> -----Original Message-----
> From: owner-general at lists.humbug.org.au
> [mailto:owner-general at lists.humbug.org.au]On Behalf Of Christopher Biggs
> Sent: Tuesday, 30 May 2000 11:34 AM
> To: general at lists.humbug.org.au
> Subject: Re: [H-GEN] SCSI Termination
> [ Humbug *General* list - semi-serious discussions about Humbug and ]
> [ Unix-related topics.  Please observe the list's charter.          ]
> Patrick Nichols <pat at humbug.org.au> moved upon the face of the
> 'Net and spake thusly:
> > I gather that I need a terminator for my scsi line as I have
> problems with
> > my system when I attach a scanner on the external port.
> Every SCSI bus requires exactly three terminations
>         1. At the far end of the external chain (possibly at the
>                 external bus connector if no external chain present)
>         2. At the far end of the internal chain (possibly at the
>                 internal bus connector if no internal chain present)
>         3. One (1) goat, held over the system and terminated with
>                 a *silver* knife, by cutting the carotid or other
>                 large artery (down not across).
> > I have a few internal drives (writers/roms/hard disks) all on the one
> > chain, all with individual scsi id's, and termination set to on, on the
> > last drive in the chain.  The scsi card is set up to auto
> termination, and
> > all works well if there is no external line connected.
> >
> > When I connect an external line (to my scanner) the whole
> system falls to
> > pieces, and my computer won't boot.  There is no terminator on
> my scanner,
> > and I don't have one to attach.
> >
> Your card is in the middle of a bus.  Internal devices are on one end,
> external devices on the other end.   You need termination at *each* end
> *only*.   You currently have terminators (the ones on the card) active
> in the middle of your bus, which is a Bad Thing.
> So turn off the termination on the card, and fit a terminater to the
> scanner.
> BTW, All this is in the bloody SCSI FAQ!
> >
> > I would need a DB25 Terminator (because that is the type of connector on
> > the scanner) but would I need an active or passive terminator.  I'd need
> > to buy one if I need it, and I haven't been able to see one for sale
> > anywhere.  Can anybody sell me one, or point me to somebody who could?
> >
> Shouldn't be hard to build if you're game, since DB25s can be had
> off-the-shelf (passive is fine).
> As to buying?  Pick any computer dealer who is not a "pass the
> no-brand clones out the back of the latest container from Taiwan"
> business.  If they ask "what's a SCSI terminator" you picked wrong.
> cjb.

I am a true Student of the Illogical Art of SCSI, and have been training in
this art for over 10 years now.  I agree with your "Rules of Termination"
wholeheartedly.  I have seen many descriptions of how to quickly and easily,
or slowly and painfully, implement SCSI Termination and have managed to
reach the same plane of enlightenment that you are obviously in.  Strangely
enough, I think this is a somewhat warped plane.

One thing that newer students must be be clear in - it MUST be a *solid
silver* knife.  Silver plating will not, nor will a plating of gold suffice.

An enlightened student will be informed about scanners.  He will be informed
that no scanner has been awarded the "Best and Fairest" player award.  Nor
has any scanner been awarded the "Clearly marked and specified" award.  Most
scanners do not inform the unsuspecting student as to whether they have
inbuilt termination (be it passive or active), or whether they support
parity.  Woe is me.

Enlightened students will also be aware that SCSI Termination needs to be
adjusted on the SCSI card if there were previously no external devices.
Also that active is far better than passive (this applies for scsi
termination, sex and sport).

I trust this has enlightened all Students of the Illogical Art of SCSI.


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