SCSI Terminators

SCSI Terminators

Post by Graeme Moff » Wed, 05 Feb 1992 10:00:53

When adding a 3rd party (ie Seagate) external drive to an RS6000, can the
drive's internal termination be used, or is it necessary to use an external
IBM one?
There was a SCSI E.C. for early models, which I understand involved only
changes to terminators (& cables), but what exactly was the change?
(technically - I know the old are black & the new are grey).
The external 60 pin terminator has apparently not changed, am I correct in
assuming that the 50 pin external device one has?


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SCSI Terminators

Post by Jean-Francois La » Thu, 06 Feb 1992 15:09:25

Quote:>When adding a 3rd party (ie Seagate) external drive to an RS6000, can the
>drive's internal termination be used, or is it necessary to use an external
>IBM one?

I have one data point (a 320H) that would (repeatedly) corrupt it's root disk
as soon as a terminated Seagate drive was added to the bus as a second disk.
The cure for this ailment involves booting from diskette, fscking the damaged
root (it had corrupt logs, in fact, always), continuing to disk, and
fixing the logs on the root you're running on (eeek!) before rebooting (the
log fixing utilities are not on the diskettes).  No fun.

External termination cured the problem for us.  We're rather happy to have
found out about the problem here rather than during a field install of a disk
(our experience with other brands of computers had led us to routinely
terminate on the last drive, which is jumpered to provide terminator power).

IBM 2nd level support could not provide me with an explanation as to why
the IBM SCSI bus would so vehemently object to termination on the drive.
Anyone know for sure?

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1. sanity check on scsi terminator settings, please

Hi All,

I've got a Compaq DeskPro with a integrated AM73C974 scsi controller.  The
problem is that I keep getting i/o errors with the disks while installing
RH7.2.  I heard once that wrong scsi terminator settings (or drive parity
settings) on the scsi chain can cause inconsistant reads and writes.  Is
that true?

I have on the cable (in order from the controller on out):

controller at id:12
scsi hard disk a at id:4
scsi CDROM at id:2
scsi hard disk b at id:0.

I have the terminator on disk b since it's on the end of the chain and it's
set to get terminator power from the drive.  There's no way I can tell if
the scsi controller itself has to be terminated - I doubt it.

I ran Seagate OnTrack Diagnostics on the two drives and there were no errors
on the surface scan.  My root file system is 1048Meg and this doesn't
include the various mounts on other partitions for /usr/local, /var, /tmp,
etc.  So, I should have LOTS of disk.

Any ideas would be appreciated!

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