SUMMARY: internal drive termination

From: Frank Cusack (
Date: Fri Dec 05 1997 - 15:56:26 CST

The original question was how to terminate internal drives on Suns.

Thanks to all the respondents:

Gene Rackow <>
Jeff Woolsey <>
Glenn Satchell<>

In general, a SCSI bus needs to be terminated at both ends (we all knew
this already). The question is whether or not this termination is provided
automatically or not. I think we can assume that the controller provides
termination if it as at the end of the bus, which is the case if there are
/either/ no external drives present /or/ no internal drives present.

If you attach external drives, the last one in the chain must be
It appears you should not terminate any internal drives in Suns.

A special thanks to Jeff Woolsey for the following:

>Sun's Field Engineering Handbook shows all 3.5" drives with explicit
>instructions to remove the terminators.

I ran a (probably doesn't qualify as extensive) test with an SS2 with
two internal drives. In one case, I had no termination, and in the second
case I had both drives terminated. I booted from one drive and mounted
the other on /mnt. I then copied /usr over to /mnt (find | cpio). I
figured this would give a lot of scsi traffic and if there were any scsi
problems I would see them.

Both cases resulted in no errors. Probably my SCSI chain was too short,
I should have added some external drives. Since the case with two
terminators didn't have any errors, I didn't go on to test the two cases
with one of the drives terminated.

Since the test with no terminators was succesful, and given Jeff's
citation, I think that no internal termination is the way to go. If I
get a chance in the future, I'll retest with a long SCSI chain and
post if I find any problems.

I won't be putting together a guide since the answer is so simple. :)

The original question:

> Is there a guide (if not, someone should put one together -- maybe I
> will from the replies I get ;) ) to terminating internal drives on Suns?
> Obviously, one of the drives needs to be terminated. But which one
> (assuming your system supports multiple drives. Do any only support one
> drive??)
> I'm specifically interested in the SS2 and Ultra 1. On the SS2 I have
> been successful terminating the drive in the bay labeled "drive 0" and
> leaving "drive 1" unterminated.
> On the Ultra 1, it seems some special circuitry correctly terminates
> one of the drives (and I guess the controller sets the SCSI ID) since
> neither drive is jumpered for ID's or termination. But what if I
> add a CD-ROM? Should it be terminated or not? Actually I plan to put
> another hard drive (and fan) in the CD-ROM bay.

* I am Pentium of Borg. Division is futile. You will be approximated. *
*        PGP ID: C001AA75         -|-       *

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