SCSI Query

[Rich Morin]

> 1.  Does anybody market a box with two ports: one that accepts digital
> data at ~megabit/sec, and the other a SCSI connection?  I'm interested in
> acquiring digital data into a Sun 3/60 over it's SCSI port; RS-232 is too
> slow for my application.

The major firms in this area are:

  GW Inst., Inc., 35 Medford St., Somerville, MA  02143, 617-625-4096

  IOtech, Inc., 25971 Cannon Rd., Cleveland, OH  44146, 216-439-4091

  National Inst., 12109 Tech. Blvd., Austin, TX  78727-6204, 512-250-9119

All three firms make digital I/O subsystems.  IOtech and NI concentrate
mostly on the IEEE-488 market, however, and provide adapters for SCSI.

GW sells their product into the Macintosh arena, you'd have to do your own
SCSI software.  IOtech and NI both claim to have Sun SCSI drivers.

Be careful about the real-time requirements of the project: some boxes
provide little or no buffering, and the Sun may not be able to keep up.  

> 2.  Where can I get information on writing a very simple SCSI device
> driver for the Sun?

First, the bad news.  The Sun Microsystems Porting Reference Guide says:

  Sun currently uses the SCSI bus for disk and tape units.  Customers
  are discouraged from porting devices to Sun's SCSI because it is an
  undocumented and unsupported external interface.  Sun Consulting is
  the sole resource for customers determined to port to the SCSI.

Now, the good news.  Sun has defined a Sun Common SCSI Architecture, which
will supplant its current SCSI offerings.  The SCSA is used on the 4/60,
and will (with luck) be available for the rest of Sun's line when SunOS
4.1 arrives.  Writing drivers for SCSA looks like a pretty trivial effort,
at least in comparison to the current situation.

You may also be interested in the efforts of The Devscsi Project.  TDP has
developed a driver and support library that allows user-mode access to
arbitrary SCSI devices.  It is being shipped as part of SGI's IRIX 3.2,
and is being ported to SCSA.

The interfaces are publicly available (send a USNail address if you want
the paper), and an implementation is available for licensing.  Contact
yours truly at uunet!hoptoad!cfcl!rdm, or TDP, P.O. Box 1488, Pacifica, CA
94044, 415-873-7841 for information.