[Simh] The Missing PDP-8s

[Paul Koning]

> On Aug 13, 2019, at 12:25 PM, Richard Cornwell <rich at sky-visions.com> wrote:
> 
> Hi Bob,
> 
> 
>> ...
>> I looked at a PDP-12 implementation. It's not hard, but I really
>> didn't want to do Yet Another DECtape Simulator for Linctape. With
>> Rich Cornwell's recent work, it's clear that the DECtape controllers
>> should have been abstracted to a library ten years ago, but doing so
>> would be a major PITA, now that there are six (at least) distinct
>> implementations (PDP1, PDP18b, PDP11, PDP8 TC, PDP8 TD, KA10).
> 
>   I am more then willing to switch to a generic library. What would be
>   nice to see is something that just gave you the actual tape frames.
>   This would also allow you to format the tape. If you write it I will
>   gladly switch to it. Most of KA10 code is from your other simulators.

That would be neat.  The formatter program would be one good testcase.  Another one, a rather tricky one, would be RT11 FILEX reading PDP-10 DECtapes.  That one is strange because it doesn't used read-all as you would expect; instead it does a regular read and picks up the upper 2 bits from one of the CSRs as the words fly by.  So for that to work you'd actually have to emulate the behavior of the word by word data transfer during DMA.

	paul