9 Dec
2015
9 Dec
'15
7:06 p.m.
Noel,
Comments below:
On 12/9/15 11:50 AM, Noel Chiappa wrote:
I have the pdf for the /70, but I just ordered a
new paper copy on
Amazon, call me old fashioned :).
Yes you are correct, 5 octal digits, only
16 bits used for instructions.
OK. This is up as my next investigation
and it will be guided by
Lions'... figuring out exactly how programs get loaded in v6 and
secondarily v7.
Thanks,
Will
From: Will
Senn
my now handy-dandy PDP11/40 processor handbook
That's good for the instruction set, but for the memory management hardware,
etc you'll really want one of the {/44, /45, /70, /73, etc} group, since only
those models support split I+D. the 18 bits holding the word 000407
You mean '16 bits', right? :-) This means
that branches are to 9th, 10th, 11th and 7th words,
respectively. It'll be a while before I really understand what the
ramifications are.
Only the '407' is functional. (IIRC, in early UNIX versions, the OS
didn't
strip the header on loading a new program into memory, so the 407 was actually
executed.) The others are just magic numbers, inspired by the '407' - the
code always starts at byte 020 in the file.