[Simh] Simulating the PDP-15/76 Unichannel

[Christian Gauger-Cosgrove]

On 17 March 2015 at 12:49, Phil Budne <phil at ultimate.com> wrote:
> Johnny Billquist wrote:
>> There is a problem in that different emulators might use a different
>> layout for memory, that you somehow need to overlap when you come here.
>> And that layout can become rather weird, and how do you actually figure
>> this out.
>
> If all simulated memory access is wrapped in C macros, you can hide
> most of the ugliness, assuming you don't mind a special build of the
> simulators for each multi-processor system.  You might end up with
> four or more builds of the PDP-11 simulator: uniprocessor, 11-only
> multiprocessor, PDP-15 + PDP-11, PDP-10 + PDP-11.
>
> Since we have CPU cycles to throw away, a "memory server" process
> could solve the cache coherency problems...
>
What of putting the "memory server" process into the PDP-11 simulator,
and making it generic? That is, you could have the memory sharing
service on the '11 simulator; which you could either configure as a
the UC15, KL10 FE processor, or part of the 11/74. It's a more piece
of software to program, but much more rewarding than compiling four
different simulators, or writing four different new devices.


Also, of note, I brought some of this up back in January 2014:
<https://github.com/simh/simh/issues/96> Also discussing implementing
the card readers on the '15.


Also, other multiprocessor systems that haven't been discussed that
might be interesting to talk about are the multiprocessor KL10 systems
namely the DECsystem-1088 and DECsystem-1099, the "strange"
PDP-11/45+PDP-11/45 setup involving "fun" with UNIBUS B (not good at
explaining things, E-11 does it as one of its unsupported
configurations), and the dual-processor PDP-15 setup (two PDP-15 CPUs
and optionally an FPP connected to one MX15-B).

And while we're on the topic of interprocessor/interemulator
communications, has anyone thought of perhaps implementing the DX11
with the co-operation of the Hercules team? It might be interesting to
see what strange things could be done having the SIMH PDP-11 as a
"peripheral" to a System/370, or System/390.


-- Christian
-- 
Christian M. Gauger-Cosgrove
STCKON08DS0
Contact information available upon request.