On Feb 20, 4:08*pm, "David WE Roberts" wrote:

It is official - I am a complete dip switch.

Reset the SCSI ID from 9 to 2 and it all sprang to life immediately.

Thinking about it, I am not absolutely sure why it wouldn't work before.
My first reaction (after seeing the SCSI card software scan for IDs 0-15)
was that if it was working on a 3 bit address it would have the range 0-7 or
4 bit 0-15 so putting the address below 7 would put it in a valid range for
a 3 bit address.
This is standard for 8 bit (narrow)SCSI.
This seemed to work.
But in that case why have a dip switch with values 0 through 9?
Cheap implementation of a single dip switch which covers 10 of the 16 values
in a 4 bit address?
Cheap part which can be set from 0-9 but shouldn't be set above 6?
Doesn't seem rational on a semi-professional scanner which cost £1k when you
could go round the world on the Queen Mary for 2/6p and still have change
for the cab.

Anyway, pleased (and relieved) that it is working.
My friend is really chuffed because the test scan of a colour slide was very
good quality, and she got a semi-professional scanner for £10 plus the cost
of the SCSI card.
She will also have to cough for the VueScan software but that looks to be
money well spent as the test version drives the scanner really well and
nobody else seems to do Windows drivers for it.
At some point I may have a play under Linux but the Windows solution fits in
with her other software and all in all she has a really good scanner for not
a lot of *money.

Oh, and I tried it without the terminator (just to see) and the SCSI
software reported "insufficient termination" which showed that the
terminator was doing something.

The card was (IIRC) an Adaptec 29160N with a 50 way D type connector
externally.
Termination of the card end of the bus is handled automagically.
The scanner had a matching 50 way Centronics style SCSI port, plus another
25 way D type (which was used to terminate with a short 25 way -
Centronics style cable plus a gender bender passive centronics style
terminator) which also suggests 8 bit SCSI (see above).
So the final puzzling part is that it had one connector which could connect
to Wide, but the other connector for Narrow.
Then again SCSI I supports 25 pin D-sub and 50 pin Centronics so this points
to a SCSI I device.
So I say again why the 0-9 ID dip switch?

Just annoyed with myself that it took so long to fix a trivial
error/misconfiguration.

Thinking back to the days when we had Mac Pluses at work there were a
number of devices which seemed to have standard switches on them, even
though you couldn't use addresses above 7. SCSI address was always the
first thing to look at when troubleshooting.
As I remember it the 50 pin centronics style connector was said to be
the 'proper' one for SCSI-1. For some reason although the external
hard drives had this connector, the Macs themselves used a standard 25
way D connector - I think I still have a stash of cables to interface
between them (and various other SCSI bits, if anyone's interested).
There were a few other things that used a 25 pin D connector for SCSI
- does anyone else remember zip drives? They were a real trap for the
unwary, since the version for use with the parallel port of a PC used
exactly the same connector - I think the only indication was the
presence of a SCSI ID switch of some sort.