memory map for RT-11 v 5

[william degnan]

On Jul 24, 2016 8:58 AM, "Jerome H. Fine" <jhfinedp3k at compsys.to> wrote:
>
> >On Wednesday, July 20th, 2016 at 18:02:44 - 0400, william degnan wrote:
>
>> Is there a minimum memory requirement for RT-11 v5?  I was discussing
with
>> Ray Fantini about it today, unsure...anyone know if 16K will work (from
>> 000000).
>>
>> Bill
>>
> You need to be more specific!  Starting with V05.00 of RT-11 in 1983,
> there were a total of 17 versions released up to V05.07 in 1998, including
> sub-versions V05.01B, V05.01C, and V05.04A to V05.04G of RT-11.
>
> Up until V05.05 of RT-11, RT11SJ.SYS required the least memory which
> was replaced with RT11SB.SYS for V05.06 and V05.07 of RT-11.
>
> Attempts to boot from RT11SJ.SYS under V05.00 of RT-11 with 24K
> bytes of memory were successful.  Attempts to boot with 16K bytes of
> memory were unsuccessful.  An RK05 was used as the disk drive since
> it is close to the smallest device driver.  The answer to your question
about
> using 16K bytes of memory is NO for all versions of RT-11 starting with
> V05.00 or RT-11.
>
> Attempts to boot from RT11SJ.SYS under V04.00 of RT-11 with 24K
> bytes of memory were successful.  Attempts to boot with 16K bytes of
> memory were also successful.  An RK05 was used as the disk drive.  The
> error message "Insufficient memory" is displayed, but some useful work
> might be done with just 16K bytes of memory. However, you did not
> ask if useful work being done was one of the criteria?
>
> NOTE that I used the Ersatz-11 emulator to check the above details,
> so there might be a difference with actual hardware.
>
> If you have any more questions, please ask.
>
> Jerome Fine

Thanks for the details.  I had been trying to boot rt-11 v5.3 on a 16k core
11/40 using RL11 (rl02) and it did not work.   The system was unable to
complete the initialization.  CPU diagnostics passed, I could load BASIC
papertape.  RL11 working correctly.  In this context I posted my question.

After I posted my message here I loaded up simh and emulated an 11 with
32k.  RT-11 v5.3 disk boots.  When I re-built the system and reduced to
16k, I could not boot, bombed.

One thing to remember is 16KW in a pdp11 is not the same thing that simh
refers to when one sets the CPU to 16K.  WWW do not all make this
distinction clearly.  I get it, just making this comment for future readers
of this thread.

Bill