RT11 sysgen and disk partitions

Jerome H. Fine jhfinexgs2 at compsys.to
Thu Mar 10 20:55:10 CST 2005

 >Gordon JC Pearce wrote:

>> Jerome Fine replies:
>> Once done, the SET command values are held in the
>> DU.SYS device driver file.  You do NOT need to
>> do the SET commands each time.  Probably not
>> recommended in any case.
> Ahaaa... Is that saved in DU.SYS when you issue the commands, then? Makes
> sense.  I'll try it when I get home.

Jerome Fine replies:

Also, if the device driver is LOADed (or Resident - i.e. system device),
then the SET commands for DU(X).SYS will not take immediate effect.
Some device drivers do, but DU(X).SYS do not.  You must
first UNLOAD or BOOT.  If the SET commands prevent a BOOT,
you are stuck until you can fix them from off that partition.  If you
need help, I can suggest a way.  Easy, but time consuming and
open to an error in some cases.  So be careful if you are making
changes to any bootable device drivers for any RT-11 partition.

>> Assuming you are booting from an RL02, then the
>> DU.SYS device driver my be LOADed for a bit faster
>> response after the first usage.  In addition, I
>> strongly suggest you use RT11FB rather than RT11SJ
>> unless the added size of the RT11FB monitor has
>> a serious impact on the program which you run.
> Well, the idea is to load TSX-Plus over it, which requires the SJ 
> monitor.

I think that FB will work as well in most cases, but NOT RT11XM!
If you first:
and then try "RUN  TSX", you will find out.  You may need to
UNLOAD other device drivers.

>> In addition, it would be helpful to know the full
>> version number of the RT-11 version which you are
>> using.  Based on the above SET commands, it must
>> be at least V05.03 or RT-11 which was released
>> in 1985.  There are certain features which later
>> versions of RT-11 have that you may wish to be
>> aware of.  the RT-11 command:
>> will provide the information, as will the banner
>> when RT-11 first boots.
> On bootup, and in SHOW CONFIG, the version is given as 5.00.

Something is VERY wrong!!  RT-11 partitions were NOT possible
until V05.03 of RT-11 in 1985.  Can you please confirm the RT-11
version number?

>> Finally, I strongly recommend against the SET
>> values which have been suggested since they
>> impact very negatively with regard to booting
>> RT-11.  You will not lose anything with a
> Ok, why is that?

If you do decide to boot RT-11 directly on power

up, the required set command is:

The code in the EPROMs for a hardware boot of DUn:
will ONLY boot physical drive "n".  Under RSX-11
and RSTS/E where hard drives do not have partitions,
the above SET command does not exists, so there is
no conflict.  In RT-11, the user is allowed to map
"unusual" relationships, so you need to understand
the reasons and the restrictions.

RT-11 is NOT able to do a hardware boot on a non-zero
partition.  (Until V05.06 of RT-11, the distributed DEC
monitors could not do a software boot of a non-zero
RT-11 partition due to one missing instruction in the
boot program.)  (Also until V05.03 of RT-11, the
SET commands for DU did NOT allow RT-11 partitions.)

Assuming you have one DU hard drive and an RX50, you
want to use (to be able to do a hardware boot):
SET  DU0:  PORT=0, UNIT=0, PART=0  (for the hard drive)
SET  DU1:  PORT=0, UNIT=1, PART=0  (for the first RX50)
SET  DU2:  PORT=0, UNIT=2, PART=0  (for the second RX50)

Thereafter, the choice is yours.  I usually recommend:
SET  DU4:  PORT=0, UNIT=0, PART=1  (second RT-11 partition)
SET  DU5:  PORT=0, UNIT=0, PART=2  (third RT-11 partition)

Remember, until V05.06 of RT-11, you can't boot DU4: or DU5:

The above information applies to distributed DEC software.
I have fixed some of the early versions, but it is of
interest very rarely and only to software fellows who use
very large hard disk drives.  I finally managed to obtain
some Hitachi ESDI DK515-78 600 MByte hard drivers which
manage 20 RT-11 partitions EACH.  The Maxtor XT8760E also
had that capacity as well.

I hope this helps.  Ask some more if you have other

>> different combination of SET parameters, but
>> you will gain with respect to what drives
>> can be booted, in particular from a cold start.
> In this instance I want to boot from a "clean" install of RT-11 from DL0,
> but eventually I will be booting from DU0.

You ca experiment with the correct values of the SET commands
while you BOOT from DL0:, after which you can copy the
DU(X).SYS file to the DU partition along with the monitor
you are going to use.  The command:
with then set everything up on the DU partition.  As long as
the DL0: partition is still available, then any mistakes can
easily be corrected when you BOOT from DL0:  A word
of caution is to never change both at the same time.  As long
as you can boot from one, it will be possible to fix things.

You can also use VM: as a temporary RT-11 partition
and experiment separately with RT11FB and RT11XM
since the device drivers are separate.  You can copy
all the *.SYS files to VM: and then:
even if you were running RT11FB as long as you make sure
that the "base" for both VM.SYS and VMX.SYS are identical.
With a 4 MByte memory on the PDP-11, there are 4096 blocks
available using just 2 MBytes of the PDP-11 memory or much
more than needed for all the SYS and SAV files, let alone other
files for a working RT-11 system.

>> The exact nature of which disk drives are being
>> used will also help.  I suspect an RD53 and an
>> RX50, but please confirm.  Most novice RT-11
> OK, this is where it gets tricky.  I'm not totally sure how to identify
> the ST506 drives fitted to the machine.  One is a full-height 5.25" 
> drive,
> with (seemingly) about 65,000 blocks on each partition.  The other is
> half-height, with considerably less on each partition - one is around
> 40,000 blocks, one is around 16,000 blocks (if I remember correctly - I'm
> not actually near the machine right now to check).  The smaller drive is
> made by Fujitsu, may be something like M224XAS ?  The label is rather 
> hard
> to read.

It sounds like you have a non-DEC controller which emulates
MSCP.  I use and ESDI version myself with Hitachi DK515-78
600 MByte drives with 600 MBytes.  The controller is the Sigma
RQD11-EC quad ESDI controller which can handle 4 ESDI hard
drives.  The RQD11-EC emulates MSCP under RT-11.

> The other drives are an RL02 (I have two but lack the cable that links 
> the
> two drives) and an RX02.

That should be easy to fix.  I suggest you ask on
the list for an extra cable.  I seem to remember that
the cable you need is the same as the normal cable
(that you are probably using right now) between the
part attached to the 40 pin cable that is then
attached to the RL02 controller at the other
end.  Just move the terminator to the bottom connector
on the second drive and connect the first RL02 drive
to the second RL02 drive - connect the bottom connector
on first drive to the top connector on the second drive.
It is usually sufficient under RT-11 to have 2 RL02
drives if you have a few spare RL02 media for backup.
A TK25 is also not bad, but MSCP drives, especially
an MSCP magneto optical such as a Sony SMO S-501 is
really great.  Unfortunately SCSI Qbus host adapters
are still a bit expensive.  I would never use a TK50
as a backup drive since comparing the file written to
the TK50 tape with the original file takes too long.
A TK70 is acceptable.

Sincerely yours,

Jerome Fine
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