Software for small-memory PDP-11s?

Jerome H. Fine jhfinedp3k at
Sat Nov 14 09:07:24 CST 2015

Sorry I forgot to remove the SPAM  KEY notice thsat my e-mail places 

 >Paul Koning wrote:

>>On Nov 13, 2015, at 5:45 PM, Josh Dersch <derschjo at> wrote:
>>Hey all --
>>Now that I have my PDP-11/05 running nicely, I'm curious what others are
>>running on small systems like this -- until this point I've only played
>>with larger (i.e. at least 28KW memory) systems.  I have only 8KW of memory
>>(with no viable options for expansion) and there's not much out there that
>>I've found.  There's paper-tape BASIC (which is always fun) and FOCAL, and
>>PTS-11 ( which is pretty cool
>>if a bit cumbersome.  Any other suggestions?
>>I'm also curious if any version of RT-11 that supports the TU58 could be
>>made to run on this system -- I have two SLUs in the system so in theory I
>>can boot from an emulated TU58. However RT-11 4.0's SYSGEN manuals suggest
>>that 12KW is the minimum supported (and experimentation bears this out) and
>>I can't find much in the way of manuals for RT-11 V3B -- which I believe is
>>the earliest version with TU58 support.  (V3B seems to be different enough
>>from later versions that I'm not quite sure how the SYSGEN process works.)
>RT11 V2 SJ will certainly fit easily in that size memory.  DOS will fit even in 4K (at least the older versions).  Come to think of it, RT might also; I haven't tried it that small.
>	paul
NOTE:  I don't have a real PDP-11/05.  All my tests
were done under Ersatz-11.

I just tried to boot V04.00 of RT-11 on a PDP-11/05
using an RK05 device (RK:) under the RT11SJ.SYS
monitor.  First I set the memory to 32 KB (16KW)
and it worked quite well.  Then I tried with 16 KB
(8KW) and while it did boot, during the boot process
of V04.00 of RT-11, I did see the error message:

Insufficient Memory

On the other hand, I was able to perform a DIR
and a few other tests which did work.

I then attempted to confirm with V2 and 16 KB of
memory and that also worked with the RK05 device.
Obviously, it is not possible to do very much with
just 16 KB (8KW) of memory.

As for support for the TU58 device (DD:), I also
attempted that and came up empty. using V3B
of RT-11.  The V3B distribution which I have
does not seem to support the TU58 since RT-11
crashes when I attempt to use the TU58 device.

There may be some bad code in RT-11 when the
TU58 is used with a PDP-11/05.  I just don't have
the resources in the time that is available to find out.

Josh, you don't mention if you have a disk drive
of any kind on the PDP-11/05,  It would help
if you could describe all of the available hardware.
If the TU58 is the only "disk drive" available, then
I am not sure what to suggest in order to get RT-11
to run in any case.

Jerome Fine

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