[Simh] TMXR/UC15 documentation?

[Mark Pizzolato]

On Tuesday, July 17, 2018 at 1:30 PM, Lars Brinkhoff wrote:
> Mark Pizzolato wrote:
> > Lars Brinkhoff wrote:
> >> The ITS restoration team is getting ready to hook up eight
> >> (simulated) Unibuses to a (SIMH) PDP-10.  The MIT AI KA10 machine
> >> really did this, and we want some of the applications that used these
> >> capabilities.
> >
> > TMXR is the simh library which is used by terminal mux devices to
> > provide telnet connections to simulated serial ports.  It is also used
> > by several point-to-point network devices (DMC11, DUP11) to connect
> > independent simh instances via simulated WAN connections using TCP or
> > UDP for data delivery.
> 
> Sorry for the confusion, I must have misunderstood when I read about those
> network devices.  Though I suppose what I want could be considered a form of
> point-to-point communication.
> 
> > What devices are going to be connected to all of these Unibus(s)?
> 
> It's mostly used to allow direct access to PDP-11 main memory.

Mostly???  What else besides memory access?  Is the access from the PDP10 
side done by programmed I/O (i.e. referencing addresses in the Unibus 
address space), or by some DMA engine which allowed transfers from the 
PDP10's memory to the PDP11's and back?

> Maybe a longer explanation is in order.
> 
> The MIT AI PDP-10 had a special device attached called the Rubin 10-11
> interface.  It allowed connecting up to eight PDP-11s.  The interface mapped
> the PDP-11 memories into the PDP-10 address space.  As far as I know (there's
> not much in the way of documentation), there was only shared memory, no
> interrupts or any other features.  The PDP-10 always initiates accesses.  The 11s
> could not access PDP-10 memory.

Given this explanation, it would seem that you're merely looking for a shared
memory model, and not really a point-to-point WAN situation.

What PDP11 model(s) were involved?  Was there a PDP11 memory map involved?

You've got the software which ran on the PDP11's?

What devices existed on the PDP11's?

The UC15 simulator is a particular PDP11 simulator which has a specific model
PDP11 and a limited set of devices.

Given that what you've got is one way with only the PDP11's memory being 
accessed and no interrupts it would seem that a KA10 with a set of PDP10 
Unibus(s), with each connected directly to a different PDP11 system, you 
could model this pretty easily. 

- Mark