[Simh] Custom ROMs on PDP-11 sim

[Bob Eager]

On Sat, 16 Dec 2017 15:42:59 -0500
Paul Koning <paulkoning at comcast.net> wrote:

> 
> 
> > On Dec 16, 2017, at 6:14 AM, Timothe Litt <litt at ieee.org> wrote:
> > 
> > On 15-Dec-17 22:14, khandy21yo wrote:
> >> Can't you just load them into ram and run them from there?
> >> Rom is just non writable memory.
> >> 
> >> 
> > He could, except that these ROMs are probably in I/O space, so
> > would need to be part of a simulated device for any code to execute
> > properly[1]. 
> 
> It would make sense (and it would be very easy) to add a feature to
> SIMH to load a memory image file into what is nominally ROM in I/O
> space.  It could be made ROM from the program point of view (i.e.,
> it's loaded from the user interface but the CPU can't store there).

And has already been done for the VAX; even simulation of the slower
ROM speed.