[TUHS] Memory on Lion's v6

Warner Losh imp at bsdimp.com
Mon Feb 28 16:09:02 AEST 2022

On Sun, Feb 27, 2022, 10:51 PM Will Senn <will.senn at gmail.com> wrote:

> Does anybody know how much memory was configured on the PDP-11 that Lion's
> used for the commentary system. Here's what the book says about the system:
> ; from lions, page 1
> ; The code selection presumes a "model" system consisting of:
> ; PDP11/40 processor;
> ; RK05 disk drives;
> ; LP11 line printer;
> ; PC11 paper tape reader/punch;
> ; KL11 terminal interface.
> I usually add the mag tape, too
> ; TM10 magnetic tape - not in lions, but super handy
> It seems like he must have had an MMU and 128k memory, but I don't know.
> I'm hoping y'all remember, know, or can otherwise divine the correct value.
> I've run with no MMU - crash on boot. I've also run with less memory, but
> then cc won't build mkconf, when I have the TM10 enabled kernel loaded. As
> a reminder, his book was published in 1977.

V6 required the PDP-11 MMU. There are all kinds of code that writes
directly to the memory mapping registers. So Lions had to have had an MMU.
I'd imagine he had at least 128k of RAM, but likely not much more since the
budgets for these machines at the time in Australia was notoriously tight.


> Will
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