Subject: Re: SCSI host adaptors
To: None <port-i386@netbsd.org>
From: Andy Ball <ball@cyberspace.org>
List: port-i386
Date: 05/24/2001 03:39:17
Hello Bernd!

  BS> Between Ultra and U160 there's still Ultra-Wide and
    > Ultra-2-Wide (LVD).

I was aware of those, but none of the CD-RW drives I looked
at had a wide SCSI bus.  Perhaps that will change if CD-RW
manufacturers adopt Ultra160.

I've toyed with the idea of picking up a SCSI-2 Fast, Wide
host adaptor because I can get 1Gb Seagate Hawk drives for
about $20 (and 1Gb is spacious compared to some of the
machines I'm currently running! :-)  I would need to figure
in the cost of cabling and new host adaptors though.

  BS> I don't think that differential modes are commonly
    > used on narrow busses.

That was my impression too.  I've seen conflicting reports
about what signalling methods are used with each of the wide
standards, so I'm having to read the small print on
everything.  Unfortunately a lot of manufacturers seem to
omit potentially important information.  :-/

  BS> If he's to use SCSI disks eventually, he should
    > definitely get at least an ultra wide host adaptor
    > (almost all of those have a narrow connector, too, for
    > CD-ROM, CD-RW and the like, or one can use an
    > adaptor).

Perhaps I should tell him to hold off until CD-RW makers
release Ultra160 drives then, in the interests of
consistency and simplified cabling.

  BS> I recommend an NCR/Symbios based host adaptor. Those
    > are usually a lot cheaper than Adaptec, but at least
    > as good.

Thanks, that's good to know.

  BS> I have a Tekram DC-390F (Ultra Wide, 16Bit, 20 MHz),
    > based on Symbios 53C875, and now there are 2 disks,
    > CD-R and DVD-ROM on the narrow connector, and one disk
    > on the wide connector.

Are the narrow and wide connectors segments of the same bus,
or separate busses? Either way, it's another option to
consider. The only disadvantage that springs to mind is
having to run two cables.  What signalling are you using on
the wide connector: S/E, HVD or LVD?

Regards,
  - Andy.