Summary: Using Sun 3/160 SCSI board for real SCSI drive?

From: Rob Scott (zeke@mpl.UCSD.EDU)
Date: Wed Jan 13 1993 - 07:06:29 CST

On January 8, I posted:
>> I am working on an ancient Sun 3/160 to try and keep it useful (as an
>> xterminal and TeX wordprocessor) for a while longer. One of the internal
>> 70 megabyte disks failed, and the owner requested that I remove both of
>> the small internal disks and replace them with an existing Micropolis 1578-15
>> (317 megabyte) SCSI disk.
>> I have removed the two MFM drives from the upper bay, disconnected power
>> from the Adaptec SCSI <-> MFM controller, installed the Micropolis drive
>> and attached the SCSI cable from the VME backplane directly to the SCSI
>> disk.
>> When I try and access the drive, I can get to only parts of it successfully.
>> Accessing the drive always yields a large amount of message like:
>> "sd0: Excessive soft errors! Check drive."
>> Some partitions can only be partially accessed, and attempts to access
>> them meets with failure and the message:
>> "sd0h error: sense key(0x3): media error, error code(0x11): hard data error"
>> "sd0h: read retry, block 531937 (142912 relative)"
>> for various sectors.
>> The Micropolis disk is terminated, and was working properly attached to
>> a CIPRICO SCSI controller attached to this system prior to my installing
>> it internally.
>> Collective net wisdom would be appreciated for the following questions:
>> 1) Can a REAL(tm) SCSI drive be supported by the internal
>> 3/160 SCSI interface card (through the normal backplane cabling)?
>> 2) If so, do I need to change any of the DIP switches on the
>> SCSI interface board to allow it to work with a real SCSI drive
>> rather than the funky SCSI/MFM or SCSI/ESDI controller?

The general concensus was that I should have no problems using a standard
SCSI disk with the internal Sun SCSI interface card. There are several
caveats, however, and they are listed here in order of importance:

        1) most Sun-2/Sun-3 SCSI cards don't supply termination power to the
           TRMPWR line on the SCSI bus. Only very late engineering rev
           cards supply power (if your's does it will have a fuse on
           the card). Make sure that your disk is supplying termination
           power (most disks have a jumper to enable/disable this).
        2) Make sure that there isn't double termination if you leave the
           tape drive in and working. The tape drive controller card
           is usually where the termination is in these older systems.
        3) Sun/OS 3.5 probably won't work with a real SCSI drive attached
           to the SCSI card. This wasn't a problem for me, since I'm
           running 4.1.1.

After checking all of the replaceable parts (internal SCSI cable, SCSI card)
with spares to eliminate them as possible breakdown points, I re-assembled the
system as it had been with the two internal ST-506 disks on the Adaptec
controller and the Micropolis 1578 (300 meg) attached externally to the
Ciprico controller. The Micropolis disk seems to work just fine this way.
I double checked the jumper on the disk which is supposed to enable
termination power, and it was jumpered "on". I suspect, however, that there
was no or insufficient power to the terminators being supplied by the drive.
All the symptoms of this problem point to termination as the trouble, but
I had cast all the correct spells and things still weren't working. Some
things just aren't meant to be, I guess.

I eventually gave up and returned the machine to the original configuration,
since it wasn't of vital importance to have the large SCSI drive installed
internally in the 3/160 cabinet. The user can live with it as is, or can
bite the bullet and trade up to a Sparcstation LX.

Thanks to: (Benjamin Cline) (Perry Hutchinson) (Andrew Luebker)
        a Sun engineer who wishes to remain anonymous

     Rob Scott, System Administrator for the Marine Physical Laboratory
            Scripps Institution of Oceanography, UC San Diego
    Internet: Cserve: 76176,637 Voice: (619)534-5503

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