From: olson@anchor.esd.sgi.com (Dave Olson)
Subject: Re: SCSI Disk Problem? (1.6 MB Seagate) [ with SCSI error info ]
Organization:  Silicon Graphics, Inc.  Mountain View, CA
Date: Wed, 22 Jul 92 19:07:46 GMT

In <1992Jul22.122215.14420@ringer.cs.utsa.edu> senseman@lonestar.utsa.edu (David M. Senseman) writes:

| In article <njj76k8@zuni.esd.sgi.com> olson@anchor.esd.sgi.com (Dave Olson) writes:
| >In <1992Jul22.022754.10599@ringer.cs.utsa.edu> senseman@ricky.brainlab.utsa.edu (David M. Senseman) writes:
| >
| >
| >| We recently installed a 1.6 GB Seagate drive on the external
| >| SCSI connector of an Indigo XS-24 (IRIX 4.0.5). The hardware
| >| inventory is as follows:
| >
| >| 	sc0,4,0: cmd=0x1b timeout after 60 sec.  Resetting SCSI Bus
| >| 	SCSI device/cable diagnostic     * FAILED *
| >
| >You almost certainly don't have the drive jumpered to not spinup
| >until a startunit cmd is received.  When not jumpered this way,
| >various drives will not respond to commands, or will accept commands
| >but not complete them, etc.  In this case, the firmware appears to
| >be somewhat confused, since a startunit command was issued (0x1b),
| >but it timed out.  These drives should spinup in far less than 60
| >seconds.  If the drive *is* jumpered to not spin up at poweron,
| >then something is wrong with the drive.
| 
| The reference sheet stated that the "Motor On" jumpers delayed
| start-up for 16 sec TIMES the SCSI ID. At SCSI ID 4, does this
| mean that the drive, if jumpered, waits 5 x 16 sec (SCSI counting
| begins at 0?). Also it's early in the morning when I'm reading this 
| but the double negatives above mean that I should have the jumpers
| installed for delayed motor on, or should the jumpers be removed?

Those are the delayed motor start jumpers.  Don't use them.  You want
the jumper that tells the drive to *never* spin up, unless a startunit
command is issued.  The drive definitely has that capability.

| BTW, what about the 4 Spindle Index pins/jumpers for synchronization --
| are they used for anything in an Indigo? It didn't seem to matter
| if they were jumpered or not.

No.  We have no wires to provide the spindle sync signal, and no
support for it.

| >Sounds like something is wrong with the SCSI bus.  Are you sure
| >that the cable to the external drive is a real, honest to god,
| >SCSI cable, and not a cheap lookalike ;)  Seriously, some centronics
| >printer cables look just like SCSI cables, but have smaller conductors,
| >and don't always have all pins connected, particularly some of the
| >grounds.
| 
| Actually we make our own from flat ribbon cables. I'm not sure
| of the gauge -- is AWG 26 reasonable? Of course, if I have
| used the vise correctly, every wire should be connected ;-)
| Are flat ribbon cables better/worse than round ones? I will
| admit that the cable is a bit long (10 ft ?) but everything
| did work fine UNTIL we replaced a Toshiba 140 MB drive with 
| the Seagate 1.6GB.

28 gauge ribbon cable is most commonly used.  10 feet should
be OK.  Of course, ribbon cable isn't shielded, so you want
to be moderately careful where you run it.  My experience is
that making the cables in a vise is a good way to get intermittent
contacts, and even shorts in some cases.

| OOH--MAAA---GOD!....Things look worse than I thought:

Yep, that looks pretty bad...
--
Let no one tell me that silence gives consent,  |   Dave Olson
because whoever is silent dissents.             |   Silicon Graphics, Inc.
    Maria Isabel Barreno                        |   olson@sgi.com