Summary of 3rd party disks on 3100

[Dirk Grunwald]

Recently, I posted asking about attaching 3rd party disks to the PMAX 3100;
several people responded, and here's the promised summary...

Summary:

+ Yes, you can use the Wren-V (and Wren-IV) on the DEC-3100.

+ Installing on any non-DEC disk appears to require an existing DEC-3100
  system [although, see last note - allegedly comes up as generic SCSI]

+ While the Wren-V can run in synchronous mode, it will spuriously
  disconnect at times. Fix may be possible (see attached notes).

+ Wren-V has good performance:
	asynch 350 -> 1000 KB/sec
	synch 1000 -> 1700 KB/sec

+ In use at: Univ. Maryland, Univ. Miami, Univ. Colorado

It appears that booting from the external SCSI disk is possible, although
the difficultly gets mixed reviews. Li at Miami says it was difficult;
however Paul Buster @ Colorado said that he didn't have a problem.

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Longer explinations follow:
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Date: Wed, 10 May 89 16:40:46 EDT
From: angel li <angel at flipper.miami.edu>
To: grunwald at flute.cs.uiuc.edu
Subject: wren iv and v on a 3100

We have a 3100 with two Wren IV's and it was a royal pain in the ass
to load the system on them.  The crux of the problem is that Wrens only work 
in non-synchronous mode and the script that installs Ultrix only recognizes
a handful of manufacturers identification codes.

To install Ultrix on the 3100 we did the following:

1. Edit the install script and pretend that the drive type is RZnn.  To
   do this step entails rewriting the install TK50 tape on another machine.

2. Once the root partition is in place, we had to patch vmunix and
   make the SCSI driver use asynchronous mode to access the drive.

3. Once vmunix is patched, you can rebuild a new kernel after editing
   the drive descriptions.

All this took us a few days because it took some time before we found
out what to patch/edit next.  The Wren's sort of work in synchronous
mode but every so often the drive hangs the SCSI bus up and you have
to power cycle the drive.  We have lent DEC a Wren IV and they are
currently fidgeting with the drive.

Let me know if I can be of further help.


Angel

Date: Wed, 10 May 89 16:59:27 EDT
From: jim at umigw.Miami.EDU (jim brown)
To: grunwald at flute.cs.uiuc.edu
Subject: Re: third party SCSI disks on Dec-3100
Newsgroups: comp.unix.ultrix,comp.sys.dec
In-Reply-To: <GRUNWALD.89May10143915 at flute.cs.uiuc.edu>
Organization: University of Miami
Summary: Add CDC WREN to Decstation 3100
Cc: 

If you have a DEC (supported) disk, then load the system onto it,
make the following edit, rebuild the kernel, and then you can use
WREN disks on the new kernel.

Edit the file /usr/sys/data/scsi_data.c and modifiy it to include
entries for WREN IV (CDC     94171-9) and WREN V (CDC     94181-15)
disk drives as RZ55 and RZ80 type devices:

{"CDC     94181-15", 16, DEV_RZ80, SZ_DISK, sz_rz80_sizes, 
	SCSI_REQSNS|SCSI_READCAPACITY, 0 }, 
{"CDC     94171-9", 15, DEV_RZ55, SZ_DISK, sz_rz55_sizes, 
	SCSI_REQSNS|SCSI_READCAPACITY, 0 }, 

Rebuild your kernel and you will have support for these drive types.

NOTE:	the CDC wren-iv and wren-v disks and the decstation 3100
	sync scsi don't work together.  as of this writing, i haven't
	been able to make an Exabyte tape work either---i have been
	told it is an Exabyte firmware problem.

Regards,
Jim
-- 
Jim Brown, University of Miami, RSMAS/MPO
[send mail to jim at umigw.miami.edu]
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Date: Wed, 10 May 89 17:36:42 MDT
From: buster at rover.colorado.edu (paul buster)
To: grunwald at flute.cs.uiuc.edu
Subject: wren V on DS3100
Cc: buster at rover.colorado.edu

it was easy to add the Wren V to /usr/sys/data/scsi_data.c as Ricky Palmer
of DEC suggested on the net some time ago.  I used the Wren V as my boot
disk for a week or two -- now the VMS folks stole it for the VS3100s.

	[...omitted..]

-paul buster

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Date: Thu, 11 May 89 06:37:28 PDT
From: rsp%ok.DEC at decwrl.dec.com (Ricky Palmer - (603)881-0370 - ZK3-3/T74)
To: grunwald at flute.cs.uiuc.edu
Subject: Re: third party SCSI disks on Dec-3100 

Hi Dirk,
 
	It is actually very easy. I posted some mail awhile
back that described how to change "scsi_data.c" to add third
party disks. You should talk to Jim Brown in Florida. He can
help you out with your Wren installation questions.
I am looking at one of his disks now as it doesn't seem
to work very well in synchronous mode. For some reason it
periodically disconnects and never reconnects. When it does
work properly it screams. For 8K transfers (filesystem) I see
just under 1 MB/sec throughput. For 64K transfers it gets up
to about 1.6-1.7 MB/sec. Nice disk, except for the problem
I mentioned above.
 
					Ricky Palmer

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Date:  Sat, 13 May 89 02:05:40 PDT
From: amdcad!cdr (Carl Rigney)
To: grunwald at flute.cs.uiuc.edu
Subject: Re: third party SCSI disks on Dec-3100
Newsgroups: comp.unix.ultrix,comp.sys.dec
In-Reply-To: <GRUNWALD.89May10143915 at flute.cs.uiuc.edu>
Organization: Advanced Micro Devices

	[....omitted...]

That's around 600MB formatted, I think.  I plugged one of those into the
Decstation 3100 I was evaluating, and it was recognized as a generic
SCSI device just fine.  I copied over the root and /usr partitions and
booted off of it with no problem.  Faster than the DEC RZ55, and much much
cheaper.  You might want to get a DEC disk so DEC will maintain your
system, though.

I've been told you can get a factor of 3 speedup on the Wren by turning on
its read-ahead cache - increases from 350 KB/sec to 1 MB/sec.  The
details will probably show up in comp.unix.ultrix sometime soon.

The 3100 & the Wren support Synch SCSI; I don't beleive the RZ55 does.

	--Carl Rigney
	cdr at amdcad.AMD.COM
	{ames decwrl gatech pyramid sun uunet}!amdcad!cdr
	408-749-2453

--
Dirk Grunwald
Univ. of Illinois
grunwald at flute.cs.uiuc.edu