| From: | Neil Bothwick |
| Date: | 3 Jul 2001 at 16:30:55 |
| Subject: | Re: Arright, what's going on here? [SCSI update] |
Sean Courtney said,
> --- Neil Bothwick <neil@wirenet.co.uk> wrote:
>> Can you post a diagram of your layout, describing it in words only is
>> going to lead to misunderstandings.
> Well, I'll try...
If it's too difficult to draw in a couple of lines of ASCII, it's wrong.
> _____________________________________
> |
> |
> ____ | _-------------[ <-- internal SCSI terminator
>|__6_|---|]----------<
> | | \
> | | |
> | |.-------. |
> ____ || Hard |--< Leftover SCSI ports
> |__3_| || Drive | \___[____[
> |`-------'
> |
> `--------------------------------------
It's wrong. A SCSI chain must be a straight line electrically. Every
point on the chain must have exactly two cable runs running away from
it, except for the two ends, which must be terminated.
Your chain has three ends, it will never work correctly. This has been
covered several times in previous posts on this subject.
> Key:
> 6 -- external Zip 100 drive, connected to Cyberstorm external SCSI-3
> port via DB25-MD68 adaptor; drive set to unit 6, unterminated.
> 3 -- external Yamaha CRW4416SXZ CD rewriter, daisy-chained to Zip
> drive. Cable has MD50 on one end [connected to CD drive] and DB25 on
> the other [connected to Zip drive]. Termination switch on drive is set
> to "off" position. SCSI-3 active terminator is connected to CD drive
> via MD50-MD68 adaptor.
What about the length of cable with "Leftover SCSI ports"? That isn't
terminated.
>> As Steve said, try with nothing. Then add the cable with the two
>> terminators, than add devices to the cable one at a time. Checking
>> the
>> version of your cybppc.device is also a good idea. The early versions
>> were extremely fussy about cabling and termination, even legal setups
>> failed.
> Did that. Works with nothing. Works with everything but the hard drive.
> Whenever the hard drive is there, forget it.
I'm not surprised. The hard drive is unterminated, as is the rest of the
chain leading away from it. you appear to be "getting away" with the
fact that you have an unterminated trailing cable, until you add a device
to it.
As has been said countless times, you must have the basic layout and
termination right. Exactly two ends to the chain, both terminated. Until
you get that sorted, there's no point in fiddling with jumpers or even
RTFM.
Cheers
Neil
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