[comp.sys.dec] EXABYTES on PDP-11 systems.

geremin@decus.com.au (01/08/91)

Hello PDP-11 Users - wherever you are. A DECUS colleague is 
having an awkward problem with `his' PDP-11/83 system. He has 
been trying for over 6 months to get an EXABYTE type drive 
installed using 3rd party interface onto the Q-BUS.

Configuration is approximately:-
	PDP-11/83
	4 MByte Memory
	DEQNA (Note NOT DELQA upgrade)
	TSV05 Interface
	2 x Viking SCSI Interfaces for EXABYTE
		(previously tried with DILOG also).
	5 x DHV11 MUX boards
	LPV11 Printer I/F
	KDA50 with 2 x RA81.

Main problems are - management wants two EXABYTES on TWO SCSI 
Controllers, System is a factory production machine with very 
little free time available for testing, site is 300 miles from 
DEC Head Office in Australia (and 3rd party vendor), at least two 
different DEC engineers have worked on system in last year, 
system only recognises one SCSI interface, system hangs 
infrequently without proper crash, system had silly timing 
problems 12 months ago before TSV05 I/F was moved to immediately 
after DEQNA (which I know should be upgraded!), BACKUP fails 
diring DIR listing of EXABYTE after copying files (not during 
file transfer), I do not have instant access to all the hardware 
manuals for all the devices in use, nor to all the recent 
software dispatch articles for RSTS/E v9, local vendor does not 
seem to be able to get much specific info from SCSI I/F makers re 
PDP-11 systems, one respected friend in DEC Aust says that 
EXABYTES and PDP-11s are INcompatible, yet DEC field service have 
agreed to install and maintain the 3rd part SCSI boards.

I need help (as do DEC field service, the user and the vendor - I 
am talking to all three at different times) - and advice.

* Does RSTS/E v9.6/v9.7 really handle STREAMING Tape Devices 
   successfully.?
* What are real differences between VAX Q-BUS and PDP-11 Q-BUS 
   (other than increased speed on newer VAXen).?
* Does anyone have a running (and happy) EXABYTE on a PDP-11 
   Q-BUS system.?  (Is UNIBUS any better or worse).
* Is anyone using the DEC KZQSA interface (with TLZ.. device) on 
   a PDP-11 system.? (If so what config and O/S)
* How serious is the old DEQNA board (without DECNET Phase V).?
* Is there a possibly timing conflict with KDA50 on Q-BUS (as 
   there was with the UDA50 on UNIBUS with 11/70).
* What is recommended configuration for these types of 
   interfaces.? (Order on BUS etc).
* Is there a similar configuration in Australia.? (or Anywhere?)
   (Does not really have to be running RSTS/E).
* Do we need to turn OFF data-cacheing to slow down the transfer 
   rate during BACKUP.?
* Does v10 claim to cure any of these possible problems.?

Thanks to all, in advance as usual,

	PS. to Terry Kennedy, `What other questions should I be 
                              asking to get the correct answers'?
   John G.
v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v*v
 John Geremin, 	  PDP-11  SIG,		geremin@decus.com.au
 DECUS South Pacific Chapter.            phone (02) 764 4855. 
c/-  MEGATRONICS, p.o.box S-5, Homebush South, 2140. Australia.
*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*

terry@spcvxb.spc.edu (Terry Kennedy, Operations Mgr.) (01/09/91)

In article <7492.278a52aa@decus.com.au>, geremin@decus.com.au writes:
[text deleted]

  By the way, let's keep this in comp.os.rsts after this article. Otherwise
we may bore the Unix folks in comp.sys.dec 8-)

> Main problems are - management wants two EXABYTES on TWO SCSI 
> Controllers,

  Any particular reason? Seems like one controller / one drive would be
about as useful. Note that unlike VMS, RSTS/E only supports 1 TMSCP de-
vice per controller.

> System is a factory production machine with very 
> little free time available for testing, site is 300 miles from 
> DEC Head Office in Australia (and 3rd party vendor), at least two 
> different DEC engineers have worked on system in last year, 

  Sounds like a typical hard-to-solve problem 8-)

> system only recognises one SCSI interface,

  What happens if you say "HA LI" at the Start timesharing? prompt? If
you could get that forwarded to me, that would help.

  However, it's more than likely that the second interface is at the
wrong CSR.
 
> system hangs 
> infrequently without proper crash,

  While doing what? Backup? What does a ^T say?

> system had silly timing 
> problems 12 months ago before TSV05 I/F was moved to immediately 
> after 

  What sort of problems?

> DEQNA (which I know should be upgraded!),

  There is _no_ requirement to upgrade to a DELQA on any system _except_
on VAXen running VMS. However, your DEQNA should be up to the current re-
vision level, which is something like N4. However, I don't think that is
related to this problem.

> BACKUP fails 
> diring DIR listing of EXABYTE after copying files (not during 
> file transfer),

  By fails, what do you mean? Hangs? "?Fatal I/O error on device" messages,
"?Unexpected error xx in yyyyyy", or what?

> I do not have instant access to all the hardware 
> manuals for all the devices in use, nor to all the recent 
> software dispatch articles for RSTS/E v9, local vendor does not 
> seem to be able to get much specific info from SCSI I/F makers re 
> PDP-11 systems, one respected friend in DEC Aust says that 
> EXABYTES and PDP-11s are INcompatible, yet DEC field service have 
> agreed to install and maintain the 3rd part SCSI boards.

  I believe that it can be made to work. I know someone who is using similar
hardware on an '83. I will try to contact him to get more information, but I
believe he is using the CMD controller.

> * Does RSTS/E v9.6/v9.7 really handle STREAMING Tape Devices 
>    successfully.?

  Yes. There are a few bugs in BACKUP which (I believe) have been fixed in
V10.0. I've not run into any of them on my 8 PDP-11's, but others have re-
ported them. RSTS Engineering put in a _lot_ of effort to clean up BACKUP
for V10.0.

> * What are real differences between VAX Q-BUS and PDP-11 Q-BUS 
>    (other than increased speed on newer VAXen).?

  There really aren't many. Newer VAXen have imposed restrictions on things
like read/modify/write cycles to I/O space, and memory is mapped rather than
being directly on the bus, but things are quite similar. For example, some 
of the drivers in 2.x BSD Unix (PDP-11) originated in the 4.3 BSD (VAX) dri-
ver set, and were recompiled to run on the 11 with trivial changes.

> * Does anyone have a running (and happy) EXABYTE on a PDP-11 
>    Q-BUS system.?  (Is UNIBUS any better or worse).

  As I said, I believe I know someone who does. I'll check.

> * Is anyone using the DEC KZQSA interface (with TLZ.. device) on 
>    a PDP-11 system.? (If so what config and O/S)

  It's not supported. Having said that, it may very well work. If you think
you'd buy one (or more) if it _was_ supported, talk to your sales rep and
have them convey that fact to RSTS Engineering.

> * How serious is the old DEQNA board (without DECNET Phase V).?

  It works fine. The problem is that the board doesn't have enough horse-
power to deal with back-to-back packets, so the newer BI-bus Ethernet inter-
faces cause it to drop packets. When this happens, it can corrupt packets
in its buffers. The same problem will happen if you try to run (for example)
NFS under Ultrix with a Sun as a server.

  DECnet/E and RSTS/E don't throw packets at it fast enough to cause prob-
lems.

  This is only true if your board is up to rev. If it isn't, then either get
the upgrade kit (to a DELQA-YM) or get it swapped for an up-to-rev DEQNA.

> * Is there a possibly timing conflict with KDA50 on Q-BUS (as 
>    there was with the UDA50 on UNIBUS with 11/70).

  The UDA / 11-70 is related to the fact that the 11/70's Unibus is slower
than standard. I don't know of any problem offhand with the KDA.

> * What is recommended configuration for these types of 
>    interfaces.? (Order on BUS etc).

  CPU		(11/83)
  MSV11-JE	(2 Mb PMI mem)
  MSV11-JE	(2 Mb PMI mem)
  TSV05		(Tape)
  LPV11		(Printer)
  DEQNA		(Ethernet)
  DHV11 [x5]	(Serial interface)
  SCSI		(Exabyte control)
  KDA50		(Disk control)
    
  Note that this is _my_ suggested order, not the [incorrect] info in the
'83 manual.

> * Do we need to turn OFF data-cacheing to slow down the transfer 
>    rate during BACKUP.?

  I don't know. I assume this is a feature of the controller/drive. I be-
lieve the Exabyte already has a lower transfer rate than other backup sub-
systems, so I don't think you'd need to do it to lower the data rate. On
the other hand, if the controller reports sucessful write completion to
RSTS before the write completes, and then goes "Oh, I was just kidding -
that write _didn't_ work", RSTS will get _very_ confused.

> * Does v10 claim to cure any of these possible problems.?

  V10 has all the patches issued against V9.x already applied, and has ad-
ditional BACKUP fixes (as I discussed earlier). It couldn't hurt. However,
be sure you apply _all_ the mandatory patches issued in the Software Dis-
patch. These are in the [US] December, January, and [I'm told] February
issues.

	Terry Kennedy		Operations Manager, Academic Computing
	terry@spcvxa.bitnet	St. Peter's College, US
	terry@spcvxa.spc.edu	(201) 915-9381

terry@spcvxb.spc.edu (Terry Kennedy, Operations Mgr.) (01/09/91)

In article <5851@spdcc.SPDCC.COM>, jin@spdcc.COM (Jerry Natowitz) writes:
> I had the same hang problem on an 11/84 (unibus) system running RSX11-M-PLUS.
> I suspect that DEC uses the same SCSI/MSCP source code - MSCPDRV.MAC - for
> RSX, IAS, and RSTS.  I would guess that the hang problem is a failure to
> release the SCSI bus during rewind.

  I just looked at the source code for the RSTS MSCP/TMSCP stuff, and it's
just RSTS stuff. There may well be a common source set (or at least a com-
mon ancestor) for the RSX variants and IAS, but the RSTS stuff is seperate.

	Terry Kennedy		Operations Manager, Academic Computing
	terry@spcvxa.bitnet	St. Peter's College, US
	terry@spcvxa.spc.edu	(201) 915-9381