[Simh] Pdp8 terminals

[Ethan Dicks]

On Tue, Sep 6, 2016 at 1:03 PM, Johnny Billquist <bqt at softjar.se> wrote:
> Hi.
>
> On 2016-09-06 18:55, Bob Supnik wrote:
>>
>> The PDP8 simulator is more or less a PDP8/A, and its terminal
>> "multiplexor" is a KL8-JA, which implements four discrete KL8A style
>> interfaces. These are superset compatible with the PDP8/I's PT08
>> discrete interfaces, and thus TSS/8 will work. Note that TSS/8 supports
>> only four discrete terminal interfaces. To get more than four lines, the
>> configuration must have a DC08(A), a multiplexor for the PDP8/I. The
>> DC08(A) is not implemented at the moment.
>
>
> This can't be correct.
>
> The KL8JA is a single line interface, compatible with the KL8E, but using
> different hardware. You can add lots of KL8E or KL8JA interfaces to a PDP8,
> if you wanted to. Each have a different device code, and that's all there is
> to it. (Talking about the actual hardware here.) In addition, as far as I am
> aware, the programming of these interfaces are pretty much the same as the
> console interface on all other PDP-8 models as well.
>
> The KL8A was a very late device for Omnibus, which require a hex wide box.
> It is a 4 line multiplexor, but the programming interface is nothing like
> the KL8JA or KL8E. In addition, not all lines are the same. And again, you
> can add several of these multiplexers to a machine, if you want to.

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.

>> There was a significant evolution in the PDP8 family's IO controllers
>> from the original 8 and 8/I to the Omnibus-based 8/E and 8/A.

Very true.  I have a bunch of the real hardware spanning the entire
era and, yeah, Omnibus devices and pre-Omnibus devices are commonly
different (I think the console 03/04 interface is, up to the DECmate
era, the most compatible across the spectrum).

-ethan