Re: [9fans] PDP11 (Was: Re: what heavy negativity!)

["Digby R.S. Tarvin" <digbyt42@gmail.com>]

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Does anyone know what platform Plan9 was initially implemented on? My guess
is that there is no reason in principle that it could not fit comfortably
into the constraints of a PDP11/70, but if the initial implementation was
done targeting a machine with significantly more resources, it would be
easy to make design decisions that would be entirely incompatible.
Certainly Richard Millar's comment suggests that might be the case. If it
is heavily dependent on VM, then the necessary rewrite is likely to be
substantial.

I'm not sure how the kernel design has changed since the first release. The
earliest version I have is the release I bought through Harcourt Brace back
in 1995. But I won't be home till December so it will be a while before I
can look at it, and probably won't have time to experiment before then in
any case.

For what it is worth, I don't think the embarrassment of riches presented
to programmers by current hardware has tended to produce more elegant
designs. If more resources resulted in elegance, Windows would be a thing
of beauty.  Perhaps Plan9 is an exception. It certainly excels in elegance
and design simplicity, even if it does turn out to be more resource hungry
than I imagined. I will admit that the evils of excessively constrained
environments are generally worse in terms of coding elegance - especially
when it leads to overlays and self modifying code.

PDP11's don't support virtual memory, so there doesn't seem any elegant way
to overcome that fundamental limitation on size of a singe executable.  So
I don't think it i would be worth a substantial rewrite to get it going. It
is a shame that there don't seem to have been any more powerful machines
with a comparably elegant architecture and attractive front panel :)

It is sounding like Inferno is going to be the more practical option. I
believe gcc can still generate PDP-11 code, so it shouldn't be too hard to
try.

DigbyT

On Tue, 9 Oct 2018 at 04:53, hiro <23hiro@gmail.com> wrote:

> i should have said could, not can :)
>
>

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