[Simh] Pdp8 terminals

[Rick Murphy]

>
>Agreed... here are the handle numbers to help clarify what we are all
>talking about...
>
>M8319 KL8A PDP-8/A 4 channel serial I/O
>
>M8650 KL8E Asynchronous Data Control (current loop or RS232)
>M8655 KL8JA Terminal Control (UART based substitute for M8650)
>
>
>The KL8E and KL8JA are, AFAIK, not easy (or not possible?) to tell
>apart in software.  The KL8A is entirely different - the only time
>I've ever used my KL8A was with RTS-8.  I'm not sure I have any OS/8
>code that knows how to talk to it.  If it's out there, I'd love to
>read it.

I can confirm this - I wrote the TSS/8 support for the KL8A to deal 
with a customer who wanted 24 serial lines on their 8/E based system. 
That was simply too much load for the bus to support the CPU, 24 
terminal interfaces, TC08, RK8E, and 32M. Trying to keep that system 
running reliably was costing DEC a fortune... Eventually we decided to 
strip the bus, add a hex box and several KL8As. Much more reliable.

The primary KL8A user was WPS-8. Only that one site ever had KL8A 
support for TSS/8.

As for the original question - it seems quite possible to add more 
lines to the PDP-8 simulator.
Edit pdp8_ttx.c to change the TTX_LINES constant from 4 to the number 
of lines you want. Must be a power of 2. Then, make sure that the 
"ttox_unit" array has the same number of entries as TTX_LINES. I 
haven't tried this, but it looks like it should work. (A more permanent 
fix for this would be to allow TTX_LINES up to some reasonable number, 
like 32, and permanently expand the ttox_unit array to 32 entries.)
         -Rick