From: jja@kaarne.cs.tut.fi (Ahola Jari,,,OHJ,57541)
Newsgroups: comp.sys.sun.hardware,comp.periphs.scsi
Subject: Re: Problems with Fast SCSI-II on Sun Sparc 10
Date: 13 Nov 1992 17:56:53 GMT
Organization: Technical University of Tampere, Dep. of Computer Science ,Finland 
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Reply-To: jja@kaarne.cs.tut.fi
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Originator: jja@kaarne.cs.tut.fi

From article <1992Nov13.081624.764@EE.Stanford.EDU>, by craig@isl.Stanford.EDU (Craig Barratt):
> I recently added a Micropolis 1548 2GB external SCSI-II drive
> to a Sun Sparc Station 10-30.  Both the Micropolis disk and Sun
> Sparc 10 support Fast SCSI-II (10MB/sec).  Initially I connected
> the disk as the only external SCSI peripheral, and had no problems
> formatting it and building a file system.  The Sparc 10 had no
> problems booting and mounting the new disk.
> 
> Next, I connected three other SCSI-II peripherals: a Sun 1.3GB
> disk, an Exabyte 8mm tape drive, and a CDrom drive (the Micropolis
> was closest to the Sparc in the daisy chain).  The Sparc 10 would
> not boot: it hung while probing the SCSI for the Micropolis drive.
> Eventually it timed out, complaining that it didn't receive a
> response to a SCSI command.
> 

When using single-ended Fast SCSI-2 devices you'll notice that
adding more than one drive outside the box will cause problems.
This is simply because of the fact that it is not possible to get them
working because of the laws of the physics (if you're familiar with
transmission line theory you'll know why). 

> 
> I talked to someone at Micropolis and they said:
> 
>    - "Sun Sparc 10's have problems with Fast SCSI-II".
> 

It's not limited to Sun - it's because it's SCSI-2 is single-ended.

>    - "An *active* (rather than passive) SCSI-II terminator will help."
> 

It may help you if your system is just barely not functioning properly
but active termination won't help in every case.

>    - "Micropolis is tweaking some Fast SCSI-II timing to make it
>       work better".
> 
> Help!!  If things don't work with the traditional passive terminator,
> I'm skeptical that an active one would help much.  Also:
> 
>    - Where would I get an active SCSI terminator, and how much
>      would it cost?  Should I bother?
>      

Try one of the cable makers who advertise on Sun Expert etc.

>    - Has anyone had good/bad experiences with Fast SCSI-II Micropolis
>      drives?
> 

Only good experiences so far.

>    - Has anyone had good/bad experiences with Fast SCSI-II peripherals
>      on the Sparc 10?
> 

Everyone is going to have if the hook more than one external Fast SCSI-2
device and/or use longer than 1' external cable....

The only way to do this properly on a SS10 is to get a differential
Fast SCSI-2 controller (Sun makes one, and so does PTI), buy only
differential drives from now and hook them on the differential bus
and use the internal scsi controller for all the old 5 MB/s peripherals.

-jja
-- 
Jari 'jja' Ahola       | Tampere University of Technology
Kuusikonkatu 5 A 4     | P.O. Box 527, 33101 Tampere, Finland
33820 Tampere, Finland | Tel (intl) 358 31 161822 (work)/358 31 182488 (home)
Puh. 931-182488        | Net address: jja@cs.tut.fi, AHOLA@FINTUTA (BITNET)
Newsgroups: comp.sys.sun.hardware