So you're saying for a system with a MMU but no working EIS (removed for
now) and 64KW RAM (half populated M7891) you're suggesting which OS? I
still have to research the best options, RSX-11M?
I'm not sure there is one. DEC OS designers typically would assume that
they are dealing with non-broken systems. Systems with MMU all have EIS,
so an OS that requires an MMU would typically take advantage of EIS
instructions. That's the case in RSTS/E, for example.
OSs designed for non-MMU systems would also typically assume no EIS,
because they were intended for the entire PDP-11 family including 11/20 and
the like.
In other words, if you don't have an EIS that works, you're likely to be
limited to no-MMU systems because those are likely to be the only ones
whose authors avoided EIS instructions.
There may be some mixed cases, an OS where the same basic system can be
built for no-MMU as well as MMU configs. If so, there might be a way to
build an MMU=yes, EIS=no config. Or it may come with EIS=no by default
because some of its configs have to handle that and it's easier to do it
consistenly. Possibly RSX is such an OS; I don't know.
paul
OK. Hopefully I can repair my EIS board then. Otherwise it's RT-11.
b
