[Simh] Multiple telnet ports in SimH to RSTS/E 9.6

[Timothe Litt]

On 31-Dec-15 15:53, Paul Koning wrote:
>> On Dec 31, 2015, at 3:42 PM, Mark Pizzolato <Mark at infocomm.com> wrote:
>>
>> On Thursday, December 31, 2015 at 12:07 PM, Will Senn wrote:
>>> On 12/31/15 1:52 PM, Paul Koning wrote:
>>>> KMC/DUP are used for the 2780 emulation feature, which is a rather
>>>> obscure layered product -- I don't know anything about it.
>>> First, I should say that my knowledge of RSTS/E is limited to a half day of
>>> trying it out. I appreciate your telling me that you don't know anything about
>>> this particular device either. It may seem insignificant, but it helps me
>>> categorize things as I learn to know if I should know it or it is actually obscure.
>> The KMC/DUP may have been useful for 2780 emulation with real hardware, 
>> but it is ONLY there for simulator to simulator DECnet connections now.
> I wonder if it would actually work with 2780 emulation -- connecting the SIMH emulated DUP with whatever a 2780 ports looks like in a simulated IBM/360.  
No.  The KMC emulation has some hooks for non-DECnet, but the DUP
doesn't.   It knows enough to parse the commands to go into the other
modes, but doesn't know what to do with them.

The KMC emulation is a functional emulator; although it requires a
sensible microcode file (COMMIOP/DUP) to be loaded, it doesn't execute
the microcode.  There's no point in emulating the KMC-11
microprocessor.  (The check for microcode version is partly so the OS
goes thru the load process, and partly so that if someone tries to load,
say COMMIOP/DZ ucode, the failure will be obvious.)  There are some
private hooks between the KMC and DUP emulations to make things work
reasonably efficiently.

DECnet uses DDCMP, which is a character oriented counted-length
protocol.  Bisync is a character-stuffing protocol.  The bit-stuffing
protocols (e.g. SDLC, X.25) are supported by the real KDP, but not by
the emulation.

The KDP emulation can be told to introduce CRC errors once in a while,
so you can watch error recovery work and enjoy the network management tools.

Extending the KMC emulation to deal with other ucodes and/or protocols
is certainly possible.  But non-trivial.  Happy coding.

I did test the KDP emulation with DECnet on the PDP-11 (rsx) as well as
VAX and the KS10.

> As for DECnet, yes indeed.  Note though that RSTS/E does not support that combination for DECnet; the only DECnet devices it supports are DMC11 (from the start), DMV11 and DMP11 (V7.1 and up), Ethernet (V9.3 and up), and software DDCMP on terminal ports (not clearly supported but present if you dig enough (V9.6 to some extent, V10.0 in cleaner form).  So synchronous DDCMP is DMC and friends only (unless you count the Pro printer/console USART work I did as a midnight project in V9.6).
>
> 	paul
>
>
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