[Simh] The missing PDPs

[Ray Jewhurst]

I think I am going to give it a try. I think am going to start with a
Straight-8 simulator for proof of concept. Would this be worth releasing as
well? Then I will start on the PDP-5. I hope there people that would
willing to answer  my questions and in the beginning there will probably be
a lot!

Thanks

Ray

On Tue, Aug 13, 2019, 9:08 AM Paul Koning <paulkoning at comcast.net> wrote:

>
>
> > On Aug 12, 2019, at 10:17 PM, Johnny Billquist <bqt at softjar.se> wrote:
> >
> > ...
> > The PDP-12 poses a more interesting problem, as it is a dual CPU thingy
> with shared memory and two totally different instruction sets, but some
> interaction between them...
>
> I've never programmed one but I have a handbook somewhere, so from that
> memory: it's not a "dual CPU" in the usual sense of two separate engines
> running in parallel, interconnected by memory or by I/O channels.  Instead,
> it's more like compatibility mode in early VAXen, where you can flip
> between two instruction sets through a mode control.  So the basic
> structure of a SIMH cpu simulation is unaffected; what changes is that
> there are two sets of opcode interpreters.
>
> The I/O devices are also different; LINCtape is physically very similar to
> DECtape but the programming interface is rather different (significantly
> more advanced -- if I remember right, it will search for the requested
> block for you rather than putting that job in the driver software).
>
>         paul
>
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