[Simh] Additional Interfaces for the VAX780 simulator

[Mark Abene]

I'm not following the need for any antiquated ISA designs.
If you REALLY wanted to pursue designing a hardware-based synchronous
serial interface, cheaply, you would design a USB dongle with an
FTDI2232C or D and a decent microcontroller from Microchip or Atmel.
You could probably do this for well under 50 bucks.  Hell, you could
probably do it for under 20 bucks.

-Mark


Bucher Andreas wrote:
>>> 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
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