[Simh] Additional Interfaces for the VAX780 simulator

[Bucher Andreas]

> > On 4/14/09, Hölscher <hoelscher-kirchbrak at freenet.de> wrote:
> >> I would like to have two (or more) additional interfaces 
> for the VAX780
> >> simulator:
> >>
> >>  DMC-11 (for DDCMP - DECnet, would be useful for the 
> PDP-11 as well)
> 
> > How would you handle the sync-serial nature of the external 
> interface?

> > Emulating the DMC-11 at a register level is probably not so 
> hard, but
> > how do you plumb the data off the hosting machine?

Well, let's start with the emulation itself, and think about the physical interface later ...
(sorry, I'd try to do it myself also if I could, but I lack the knowledge and experience)
 
> For a start I would be satisfied if I could connect two or 
> more simh simulators (all on the same host),
> so there would be no hardware issues. 
> Later of course I'd like to connect to the outside world as well.
> I've got absolutely no clue how to do that yet.
> I hope for intelligent ideas / suggestions from other people :-))

For the first start, I'd use the Ethernet interface of the host to set up connections between two virtual DMCs. Then, if one dares, develop a plugin board for any mainstream hardware platform (but this is possibly not worth the effort - or does anybody still require a real DMC nowadays ? Alternatively, design a ISA card and hook it up using an USB-to-ISA adapter). Or, what I would prefer, to become independent of any hosting hardware: Why not use the terminal server approach ? Internally, the VAX/PDP system sees it as virtual DMC-11 (or similar), the data is converted and routed by simh via ethernet to the "bulkhead" located in a terminal-server-like device, and there you could connect the cables. This way, the PC/MAC/Alpha/Palmtop/Coffee Machine/etc. running SIMH requires just a IP network, and nothing else.
Does this sound feasible ?
 
To add my other fife cents: I'd quite like the idea of having fully "virtual" components (first), because this is a) useful for the preservation of the knowledge about the hardware, firmware and drivers (how much re-engeneering of old hardware was done for simh itself ... ?), and b) why not have a virtual environment first, and then if that exists, think about and add a "real-world" interface later.

About the CI780: Why not have it fully virtual ? Create a virtual star coupler then and hook up the emulators ...

And besides: Where's the problem connecting two of those CIs on two emulated machines via the  Ethernet interface ? If this is built into the emulator's design, CI clustering would be on hand, and 100mBit and above Ethernet should be fast enough, no ?


Or, what I would like as well: Emulated HSCs. Would make a nice addition to a CI :-)

> I must admit it is all for fun, so calling that "working" 
> does not quite hit the point ;-)

Well, that might be the case for most of the simh users ?! :-)
Still, setting up a VMS environment from scratch on several machines is hard work, anyway.

cu, 
Andreas