[SunRescue] Hi!

[Greg A. Woods]

[ On Wednesday, February 9, 2000 at 19:21:24 (+0100), Peter Koch wrote: ]
> Subject: [SunRescue] Hi!
>
> >I'm fairly certain the command set used is definitely SCSI-II.
> 
> Maybe, but all hardware looks suspiciously like SCSI-I.
> Sure the NCR 5380 can SCSI-II and thus the "si" may understand
> some SCSI-II commands. The "sc" won't!!! And the SunOS driver
> might not make use of any SCSI-II command...          

For 5MHz synchronous single-ended busses the SCSI-I hardware is
sufficient and is a legal "alternative" in the SCSI-II spec.

I don't remember for absolute certainty but I think SunOS-4 drivers will
negotiate async. with capable drives, and I am more sure that NetBSD
does.  I'm certain you need SCSI-II commands to negotiate async.

If the "sc" won't do any SCSI-II commands then it is really only worth
using on a tape drive or with one disk alone on the bus.  Anything more
will drive performance through the floor.  I wouldn't even backup that
disk to an MT02 connected tape on the same bus off-hours as it'll wear
the tape and drive out long before its time, not to mention probably
take an order of magnitude longer.

> Yeah. There were rumours that some Sun3 SCSI connectors have
> the termpower line connected to GND!!! thus killing hard disks
> if termpower is applied to the bus.
> Does somebody know more about this issue? The only thing i
> found was this:
> 
>         Check out pin #26 on the Sun SCSI bus.. It's termpwr, and on some
>         machines, should NOT be connected.. I don't know if it will
>         solve your problem, but my Sun wouldn't boot off my 1Gb DEC
>         until I cut off wire 26.

Whomever wrote that probably didn't have his drive jumpered correctly.

>         The problem is, Sun somtimes grounded that pin on several 3/60's
>         and causing improper termination power.

I've never found this to be a problem on any of my 3/60's but it could
be I suppose.  It is definitely a problem on 3/80's from what I've read
and heard second-hand.

I've seen a 3/260 with "si" controller completely fry the TERMPWR line
on a ribbon cable when the drive was accidentally rested live on the
chassis thus grounding the line.  I don't think it damaged the backplane
but it sure made a mess of the ribbon cable!  :-)  So long as TERMPWR
wasn't being supplied by the drive(s) on the bus at the time they should
have been OK too but if they were also supplying TERMPWR then some of
their power traces might have been fried too.

On a 3/60 of course the same mistake would only blow the fuse.

A simple read of the SCSI spec, and a check of the draft standard should
remove any confusion.  From there a volt/ohm meter and a bit of testing
should ascertain whether or not any given SCSI port is conforming or not.

-- 
							Greg A. Woods

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