Subject: Re: Working wide->narrow SCSI adapters?
To: None <>
From: Carl Lowenstein <>
List: port-alpha
Date: 11/02/2001 10:54:42
> Date: Thu, 1 Nov 2001 23:46:40 +0100 (CET)
> From: Anders Hogrelius <>
> To: Paul Mather <>
> cc: <>
> Subject: Re: Working wide->narrow SCSI adapters?
> On Thu, 1 Nov 2001, Paul Mather wrote:
> >
> > I have a DEC 3000/500S, which uses 50-pin narrow internal cabling, and a
> > 68-pin wide drive I want to use in it.  Does anyone know where I can buy
> > a *WORKING* adapter (preferably low-profile) that will let me connect
> > the wide drive to the internal 50-pin SCSI bus?  I stress "working"
> > because I mail-ordered one before, and it wouldn't work.  I'm guessing
> > it was wired up incorrectly, as mentioned in the SCSI FAQ.
> >
> I could check with the company i've bought my adapters from. Since i'm
> located in Sweden i could at least try to find out which brand they are.
> I've used a couple without problem in both my DEC 3000/300 and several of
> my VAX'en. I'm actually sitting here with one in front of me, but
> unfortunately there is no markings on it whatsoever, to indicate it's
> manufacturer.
> Did you jumper your drive correctly? I had to add two jumpers to switch
> my drive from LVD to single ended mode, and from wide to narrow SCSI.
> The auto mode switching of the disk didn't work. There is also another
> caveat. At least with the adapters i've got, they have to be at the end of
> the SCSI cable. They were all selfterminating, so adding a disk after them
> on the chain with a termination on it would cause problems.

As an extra added complication, this can be drive-specific.  Some
wide SCSI drives have internal pullups on the 9 extra data and
control lines, so they default to logical 0 and do not need to
be terminated when used on a narrow bus.  Some drives do not.

There should be information on this in the collected archives
of newsgroup comp.periphs.scsi.  It may be hard to find among all
the noise in that group.  Also look at < >.

        carl lowenstein         marine physical lab     u.c. san diego