Some PDP-11 info (was Re: C compilers for RSTS/E?)

From: Paul Koning <>
Date: Sun Oct 24 16:02:11 2004

>>>>> "Jerome" == Jerome H Fine <> writes:

>> Sounds a bit like a project I did at the University of Illinois
>> modifying RT11. It didn't get completely finished but it
>> worked...

 Jerome> PIC is standard in the USR since it moves up and down in
 Jerome> memory ALL the time. So I do not understand why you even
 Jerome> mention the PIC aspect, let alone that something special
 Jerome> needed to be done, although perhaps with overlays, something
 Jerome> extra was required. On the other hand, device drivers which
 Jerome> execute their overlays within the USR buffer do that all the
 Jerome> time.

Memory is a bit rusty, but I think what I did was to define an overlay
buffer (probably one or two blocks long) essentially as part of RMON.
So displacements from overlays to RMON would be constant, no matter
where RMON was loaded. Taking advantage of that saves space, because
you can reference RMON data and code without having to do it PICly --
just use PC relative addressing. However, that requires an assembler
that can be told "this code might link at X, but it will execute at

 Jerome> The only aspect I see a being a REAL difficulty is that it is
 Jerome> on hard copy. Any idea how many pages.

2-3 inches of line printer output?

Received on Sun Oct 24 2004 - 16:02:11 BST

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