Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!snorkelwacker.mit.edu!bu.edu!wang!tegra!vail
From: vail@tegra.COM (Johnathan Vail)
Newsgroups: comp.periphs.scsi
Subject: Re: Always IN-2000 SCSI host adapter (the real story)
Message-ID: <2379@atlas.tegra.COM>
Date: 7 Jun 91 19:40:22 GMT
References: <1991Jun06.204457.28453@xstor.com> <90@talgras.UUCP>
Distribution: usa
Organization: Tegra, Inc., Billerica, MA
Lines: 48
In-reply-to: david@talgras.UUCP's message of 7 Jun 91 15:46:30 GMT


In article <90@talgras.UUCP> david@talgras.UUCP (David Hoopes) writes:

   >There are some problems: first, the board uses the WD33C93A SCSI chip.
   >According to the opinion of others here more experienced with protocol
   >chips, this is "not a good chip" (stated slightly more colorfully :-).

   What is wrong with this chip.  Does it not work right?  Is it hard to
   write drivers for?  Is it the wrong color?  We use this chip on some of
   our scsi hardware and I have not heard of any trouble with them.

The color is usually OK.  Writing drivers for it is a real pain.  Ask
someone who has about the dreaded 4b status.  Not that it is a bad
chip, the real problem that I have with it is that you don't really
have a good feeling of whats going on inside.  You can't even look at
the SCSI signals.  When all is said and done it works ok.  And getting
2 interrupts (at least!) for every operation is not the greatest thing
for performance, esp with unix.

Give me a NCR 53C710 any day!

   >The second problem is much greater: the external connector is not an
   >accepted SCSI-1 or SCSI-2 connector.  It is a 25 pin Macintosh connector.

   I am sure that someone will correct me if I am wrong, but I think that the
   Macintosh style conector is an accepted SCSI-1 (I don't know about SCSI-2)
   connector.  The way I understand it there are two types of conectors that
   are covered in the spec.

OK.  The 25 pin on Macs may be a standard in the industry but are not
a real SCSI connector.  There are no 25 pin cables in the SCSI-1 or
SCSI-2 specifications.

There are several different connectors in the spec for both single
ended and differential.  Basically these are: a 50 pin header, a 50
pin "centronics", and a DB-50.  The D connector is not standard in
SCSI-1. These are for the "A" cable in SCSI-2 which is the equivelent
of "the cable" in SCSI-1.


jv


"Hackers, as a rule, do not handle obsolescence well" - Oliver Wendle Jones
 _____
|     | Johnathan Vail | n1dxg@tegra.com
|Tegra| (508) 663-7435 | N1DXG@448.625-(WorldNet)
 -----  jv@n1dxg.ampr.org {...sun!sunne ..uunet}!tegra!vail