RTEM-11 Questions

Jerome H. Fine jhfinedp3k at compsys.to
Tue Nov 9 07:39:42 CST 2010

I am attempting to enhance a program which runs under RSTS/E, RTEM-11,
RT-11 and TSX-Plus.  Thus far, I have managed to support these enhancements
for all but RTEM-11 due to the lack of documentation on RTEM-11.  When
I requested help with supporting such programs under RSTS/E, John Dundas
provided a reference document which cleared up many questions.

Does anyone know of a document (and its link if it is on the internet, 
at bitsavers) which describes the support provided by RTEM-11 for programs
which also run under RT-11?  From the comments that I have seen, the RT-11
operating system is run under RTEM-11 with special "hooks" to interface to
RTEM-11.  If my understanding is correct, then all of the RT-11 EMT requests
supported by an RT11SJ monitor will also be available when running under

There are also two other specific questions that I suspect have a simple 
(a)  How much memory does a user program have which runs under RTEM-11?
       My assumption is that a user program has approximately the same 
size of
       memory available when running under RTEM-11 as it would when running
       under the RT11SJ monitor on a PDP-11 with 64 KBytes of physical 
       which usually (when no additional device drivers are present) 
ends up being
       approximately 48 KBytes or an address range from 0 to about 
120000 octal.
(b)  Whereas RT-11 actively supports the ability of device drivers to be 
       and UNLOADed at any time based on which devices are in active 
use, RSTS/E
       and TSX-Plus require the device drivers of any device that is 
active to be
       LOADed at all times.  It would be an assumption on my part, but I 
tend to
        assume that under RTEM-11, any available devices are already LOADed
        by the actual operating system that controls the CPU.  
Specifically, if a user
        program performs the .DStatus RT-11 EMT request for an available 
        the 3rd word of the device driver information will always be 
non-zero which
        specifies that the device driver in question is always in memory 
and that a
        .Fetch RT-11 EMT request would be redundant.

Can anyone provide any documentation sources?  If anyone knows the answer
to the approximate size of memory available to a user program running under
RTEM-11 and / or the answer concerning the LOADed status of a device driver,
it would be greatly appreciated.

Jerome Fine

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