From: wang@cedar.nrl.navy.mil (Dennis Wang)
Subject: SUMMARY: SCSI-2 on SPARC-10
Reply-To: wang@cedar.nrl.navy.mil
Organization: Naval Research Lab
Date: Thu, 17 Dec 1992 15:56:08 GMT

Here is what I got back as answers to my query re SCSI-2
(Interesting that two of the responses to a nationwide broadcast come from my own domain :)

----Begin Include ----

From schuette@roadkill.nrl.navy.mil Tue Dec 15 16:40:58 1992
Return-Path: <cedar.nrl.navy.mil>
Date: Tue, 15 Dec 92 16:41:05 -0500
From: schuette@roadkill.nrl.navy.mil (Larry Schuette)
To: wang@cedar.nrl.navy.mil
Subject: Re: SCSI-2 on Sun SPARC 10
Newsgroups: nrl.misc,comp.sys.sun.hardware
Organization: Naval Research Lab, Physical Acoustics, Washington, DC
Cc: 
Content-Length: 569
Status: RO
X-Lines: 16

you cannot mix fast and slow scsi.  the drives will work, but only
at slow scsi speeds.  This is true for the Western Digital 
Version WD33C93B, revision C controllers.
(which are used on newer SGI machines)

Larry
-- 
    ----------------------------------------------------------------------
	"The quality of the kite matters little.  Success depends upon
		the man who sits in it."		BMv. Richthofen

Lawrence C. Schuette			  schuette@roadkill.nrl.navy.mil
Code 7133				  (202)767-2739  
Naval Research Laboratory		  (202)767-5561 (fax) 	
Washington D.C.	20375-5320


From buck@ra.nrl.navy.mil Wed Dec 16 10:37:32 1992
Return-Path: <cedar.nrl.navy.mil>
Date: Wed, 16 Dec 92 10:37:39 EST
From: Loren Buchanan <buck@ra.nrl.navy.mil>
To: wang@cedar.nrl.navy.mil
Subject: Re: SCSI-2 on Sun SPARC 10
Newsgroups: nrl.misc,comp.sys.sun.hardware
Organization: Naval Research Lab, Washington, DC
Content-Length: 2381
Status: RO
X-Lines: 46

In article <BzBIoq.2zC@ra.nrl.navy.mil> you write:
>Does anyone know of any problems using the SCSI-2 on a SPARC 10 ?  I am getting some
>conflicting stories.
>
>1. "No problem mixing fast SCSI-2 and slow SCSI" - Sun rep

He is probably right, no problem unless you want the speed from your fast
SCSI-2 devices.  If you mix them you will get the speed of the slowest device
on the bus.

>2. "Big problem mixing fast SCSI and slow SCSI, you should put all your
>slow SCSI devices on the SPARC 10 embedded controller and all the fast SCSI on
>a separate differential SCSI controller board (you will have to buy diff SCSI 
>drives also - about $200 more per drive). Sun really messed up with the active 
>termination on the embedded controller. " - 3rd party drive supplier

This is the correct solution.  We are ordering two HP 735s, each with one
slow SCSI and one fast wide SCSI.  There are several advantages to this
solution, the big and obvious one is fast drives on the fast bus will go
fast.  The differential bus will have significantly less errors and you will
not have to pay as much attention to your total bus length.  By putting 
your CD-ROM drive and tape drive(s) on the slow bus and your hard disks on
the fast bus you will speed up software installation and backups (although the
gain may be small depending on other factors).  Another thing to be aware of
is if you ever have a flakey device on one of the busses, by moving devices
from one bus to another you will be able to isolate the problem

>3. "No problem mixing fast SCSI and slow SCSI" - another 3rd party drive supplier

We recently bought 3 fast SCSI drives and have them all on slow SCSI busses.
They are all working well.  Another thing to be aware of is that the raw
data rate of reading from or writing to a drive is limited to the bits that
pass under a single head.  Most advertising will not mention this number.
The current crop of 2G drives probably are 5Mbytes/second give or take
750KBytes/second depending on inner or outer tracks.  You will need two or
more drives to take advantage of the fast bus.

B Cing U

Buck

-- 
Loren Buchanan (buck@curie.nrl.navy.mil) | #include <standard.disclaimer>
NRL Code 5842, 4555 Overlook Ave.        | #include <computer.graphics>
Washington, DC 20375      (202) 767-3884 | #include <electronic.music>
Phone tag, America's fastest growing business sport.

From nash%rohan@sdsu.edu Wed Dec 16 14:06:07 1992
Return-Path: <cedar.nrl.navy.mil>
Date: Wed, 16 Dec 92 11:06:16 PST
From: nash%rohan@sdsu.edu (Ron Nash)
To: wang@cedar.nrl.navy.mil
Subject: Re: SCSI-2 on Sun SPARC 10
Newsgroups: nrl.misc,comp.sys.sun.hardware
Organization: SDSU Computing Services
Cc: 
Content-Length: 879
X-Lines: 17
Status: RO

As I understand it, yes you can mix SCSI and SCSI-2 devices.  The SCSI-2
bus negotiates with each device the speed it runs - but (you knew there
was a but didn't you?!) active SCSI devices will drop the thruput of your
SCSI-2 devices to roughly the SCSI (5MB/s) rate.

It is important to keep the SCSI-2 devices close the the machine.  Total
bus length should be under 4 feet for SCSI-2 devices unless you modify
you SCSI-2 driver and terminator to use IBM's FPT technology.  I have not
used FPT, but other posts have indicated it costs about $40 per end
from Aeronics and improves SCSI-2 thruput over SUN's active termination. 

             ,--, | Ron Nash	  San Diego State University
       _ ___/ /\| | nash@sdsu.edu
   ,;`( )__, )  ~ |  
  //  //   '--;   | Gin-N-Tonic   Learning to be an endurance horse
  '   \     |     | Luv on Fire   trusty trail horse
       ^    ^

---
Dennis Wang
Solar Physics Branch - Code 7660
U.S. Naval Research Laboratory.
4555 Overlook Ave SW
Washington DC 20375-5000

Newsgroups: comp.sys.sun.hardware,mitre.sys.sun