[Simh] PDP-11 DC-11 support: help please

[Warren Toomey]

All, to follow on from the announcement that 1st Edition UNIX is now running
on Simh with the KE11A patch, Tim Newsham has also got the system running in
multiuser. This requires DC-11 support, which currently does not exist for
the PDP-11. Tim has made a "quick and dirty hack": he has modified the
pdp11_dl.c code to act like a DC-11. Obviously this is not the best solution.

The change required to support 1st Edition UNIX is small: change the unibus
address for the DL11 device, and OR a "carrier detect" bit in the CSR.

So I have a few questions:

1. I can see that the pdp11_dl.c code supports reconfiguration of the
   address. For the life of me, I can't work out the syntax to do so.
   Can someone hit me with a cluebat? Ditto for getting the output
   device into "7b" mode and not "UC" mode.

2. The proper solution would be to do a full implementation of the DC-11.
   Given that the unibus address can be reconfigured at run time, would
   it be allowable instead to add a configuration command which would
   let the user set the "carrier detect" bit?

3. Finally, the Simh FAQ says: The SIMH web site contains documentation on the
   internals of SIMH, as well as specific help for writing new peripherals for
   several of the popular simulators. Could someone point out the location of
   this documentation; I've have a look around with no luck.

Many thanks for advice, and also thanks for such a great simulator.

Cheers,
	Warren Toomey