Thanks to all the people who answered my questions. Below are
some of the responses. These contain some very useful overviews of
the two types of SCSIs availabel on an SS10.
We have not had any trouble putting older Sun 600 Mbyte disks on the
Fast SCSI. We also have some 2.1 Gbyte disks on the differential
SCSI. Everything seems to be working fine.
Regards,
Joe Picone
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
X-Delivered: at request of picone on trdc000
Return-Path: <cdr@kpc.com>
From: cdr@kpc.com (Carl Rigney)
Date: Mon, 5 Apr 93 07:23:04 PDT
To: picone@trdc.ti.com
Subject: Re: Help: SS10 Differential SCSI
Newsgroups: comp.sys.sun.hardware
In-Reply-To: <PICONE.93Apr5161614@trdc001.trdc.ti.com>
Organization: Kubota Pacific Computer Inc, Santa Clara, CA
In article <PICONE.93Apr5161614@trdc001.trdc.ti.com> you write:
>(I am sure these have been answered before, but I would like
>verification from "an expert". Our local Sun support claims
>differential SCSI and standard SCSI are not compatible.)
And is absolutely correct. By the way, the proper terms are
differential SCSI and single-ended SCSI - both are standard.
>Does anyone know the answers to the following:
>
>1. It appears as though an SS10 contains one standard SCSI on which
> the internal disk is installed. Is this correct?
> "Standard SCSI" seems to be Sun's term for the SCSI found on Suns
> prior to SS10s (SCSI-I I believe).
The internal disk and built-in external SCSI port on the SS10 are
10MB/sec single-ended Fast SCSI-II. It works fine with 5MB/sec
synchronous SCSI devices and 1.5MB/sec asynchronous SCSI devices.
We've found that Fast SCSI is much more sensitive to noise when its
single-ended, so for Fast SCSI you really want Differential to get
best results. Using Active or Forced Perfect Termination instead
of passive termination on your single-ended SCSI bus is almost as good
if you don't need long cable lengths. Sun sells an active terminator.
FPT slightly violates the SCSI spec, so I'd stay away from it on general
principles.
Single Ended SCSI allows up to 6 meters of cable, but you have to
include the cable lengths inside enclosures, which can add a lot!
In practice, I've heard of problems with Fast Single Ended SCSI with
passive termination when used beyond 2-3 meters.
Differential SCSI allows up to 25 meters.
>2. One of our SS10s (trdc014) contains one internal standard SCSI and two
> external differential SCSIs (S-bus cards). The differential SCSI
> uses a new style of connector. It appears to be the same style
> of connector as the SS2, but contains more pins.
It's a 68-pin wide SCSI connector. Sun's DSBE/S card (what you
probably have) doesn't support wide SCSI as far as I know, but I think
Sun did the right thing by using a connector that can't be plugged into
a single-ended 50-pin micro-SCSI connector, because the results can be
disastrous.
(Wide SCSI transfers 16, 24 or 32 bits instead of 8 at a time, but
is currerntly very rare. Fast SCSI is 10MB/sec with 8 bits. The
SCSI II spec defines all the way up to Fast Wide 32-bit SCSI for
40MB/sec.)
> (a) Can I put standard SCSI disks on a differential SCSI bus?
> The answer should be yes.
The answer is definitely no.
>3. Third party Devices developed for the standard SCSI should work
> on the differential SCSI, correct?
> (The answer we were told is yes.)
Most modern disk drives are available in both single-ended and
differential versions at about the same cost. You *cannot* mix them on
the same bus. DSCSI disks are much rarer than Single-ended SCSI but
will become more popular. Almost all non-disk SCSI peripherals are
still single-ended.
>4. Can I mix standard SCSI devices and differential SCSI devices on
> the same bus?
Absolutely not.
It sounds like perhaps you wanted to buy Sun's Fast Single-ended SCSI and
Buffered Ethernet card (the FSBE/S), instead of the DSBE/S cards.
Here at KPC we have a lot of single-ended SCSI disks, but all future
disks purchased for our fileservers will be DSCSI, because it's more
resistant to noise and can be run longer distances. We're using
the micro-68 thumbscrew connectors for all DSCSI so they can't be
plugged into the micro-50 SCSI by mistake.
-- Carl Rigney cdr@kpc.com-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- X-Delivered: at request of picone on trdc000 Return-Path: <Shane.Sigler@corp.sun.com> Date: Mon, 5 Apr 93 08:49:40 PDT From: Shane.Sigler@corp.sun.com (Shane Sigler) To: picone@trdc.ti.com Subject: Re: Help: SS10 Differential SCSI Content-Length: 2462
Joe,
Comments are inserted.
In article 93Apr5161614@trdc001.trdc.ti.com, picone@trdc.ti.com () writes: >(I am sure these have been answered before, but I would like >verification from "an expert". Our local Sun support claims >differential SCSI and standard SCSI are not compatible.) > >Does anyone know the answers to the following: > >1. It appears as though an SS10 contains one standard SCSI on which > the internal disk is installed. Is this correct? > "Standard SCSI" seems to be Sun's term for the SCSI found on Suns > prior to SS10s (SCSI-I I believe). Internal disk devices in the SS10 as with all desktop Sparcstations are all on the internal hostadapter. Starting with the SS10, Classic and LX the internal host adapter is a 10Mb/sec Fast SCSI bus, all previous ones were 5Mb/sec buses.
> >2. One of our SS10s (trdc014) contains one internal standard SCSI and two > external differential SCSIs (S-bus cards). The differential SCSI > uses a new style of connector. It appears to be the same style > of connector as the SS2, but contains more pins. > > (a) Can I put standard SCSI disks on a differential SCSI bus? > The answer should be yes. No, for 2 reasons, the connector on a DSCSI (differential) is 68 pins not 50, secondly they are electrically incompatible. The DSCSI will allow cables lengths up to 25meters as opposed to the 6meters for standard SCSI. > > (b) What cable or connector do I need (part number)? For which the DSCSI or non-DSCSI? > >3. Third party Devices developed for the standard SCSI should work > on the differential SCSI, correct? > (The answer we were told is yes.) Again this is no for the same reason as 2a. > >4. Can I mix standard SCSI devices and differential SCSI devices on > the same bus? See 2a. >
Hope this helps, Shane
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- X-Delivered: at request of picone on trdc000 Return-Path: <hanson@pogo.fnal.gov> Date: Mon, 5 Apr 1993 10:56:59 -0500 From: Steve Hanson <hanson@pogo.fnal.gov> To: picone@trdc.ti.com Subject: Re: Help: SS10 Differential SCSI Newsgroups: comp.sys.sun.hardware References: <PICONE.93Apr5161614@trdc001.trdc.ti.com> Reply-To: hanson@pogo.fnal.gov Organization: FERMILAB, Batavia, IL
In comp.sys.sun.hardware you write:
>(I am sure these have been answered before, but I would like >verification from "an expert". Our local Sun support claims >differential SCSI and standard SCSI are not compatible.)
>Does anyone know the answers to the following:
>1. It appears as though an SS10 contains one standard SCSI on which > the internal disk is installed. Is this correct? > "Standard SCSI" seems to be Sun's term for the SCSI found on Suns > prior to SS10s (SCSI-I I believe). Well, the SCSI bus that is built in to the 10 is a FAST SCSI bus - it's 10 Meg rather than the 5 meg bus on the older machines.
>2. One of our SS10s (trdc014) contains one internal standard SCSI and two > external differential SCSIs (S-bus cards). The differential SCSI > uses a new style of connector. It appears to be the same style > of connector as the SS2, but contains more pins.
> (a) Can I put standard SCSI disks on a differential SCSI bus? > The answer should be yes. The answer is no - you'd at least have to put in a differential to single-ended converter for the single-ended part of the bus.
> (b) What cable or connector do I need (part number)? You need a converter as well as the cabling. You'd probably be much better off just to use single-ended host adapters for the single-ended peripherals.
>3. Third party Devices developed for the standard SCSI should work > on the differential SCSI, correct? > (The answer we were told is yes.) They lied to you. >4. Can I mix standard SCSI devices and differential SCSI devices on > the same bus? Well, no, not really. > >Thanks in advance.
-- Steve Hanson - FERMILAB, Batavia, Il. hanson@pogo.fnal.gov or hanson@fnal.fnal.gov
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- X-Delivered: at request of picone on trdc000 Return-Path: <birger@vest.sdata.no> Date: Mon, 5 Apr 93 18:42:04 +0200 From: birger@vest.sdata.no (Birger A. Wathne) To: picone@trdc.ti.com Subject: Re: Help: SS10 Differential SCSI
The on-board SCSI is a SCSI-2 with the fast option (10Mb/s). This one is completely compatible with the SCSI on older Sun's.
Differential SCSI is *not* hardware compatible with non-differential. You cannot use your old drives on differential chains.
If you were told that ordinary SCSI would work on differential chain's complain to whoever told you so. You can mix fast and slow units on the built-in or SBus non-differential SCSI chains. But you cannot mix differential and non-differential, as they have completely different signals.
With proper (active) terminators on the SS10 on-board SCSI, you should be able to run anything you want. There should be no reason to use differential cards. I would exchange them for Sun's fast SCSI with buffered ethernet.
Birger A. Wathne Email : birger@sdata.no | Until Sept. 9. 1993 From Sept. 9. Private: Fjoesangervn. 133, N-5032 Minde | Tel: +47 5 200062 (+47 55 20 00 62) Work : Skrivervik Data A/S | Tel: +47 5 543740 (+47 55 54 37 40) Thormoehlensgt 55, N-5008 Bergen| Fax: +47 5 322853 (+47 55 32 28 53)
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