[Info-vax] Exquisite timing! (Was: Re: sending out a VMS update next week)

[Mike Rechtman]

Richard Maher wrote:
>  Jordi Guillaumes i Pons <send.me at no.spam> writes:
>> En/na VAXman- @SendSpamHere.ORG ha escrit:
>>> Envision Rod Sterling walking out from the background darkness into the 
>>> shadowy light, camera focused on him from his lapel and tie, and with a
>>> cigarette lit and its smoke encircling his head...
>>>
>>>     "Picture, if you will, a man who has just consumed too much wine 
>>>      or too much LSD or who has simply fallen squarely upon his pate
>>>      from an appreciable height, and is now totally delusional in the 
>>>      usenet newsgroup of comp.Twilight.Zone..."
>>>
>>> Where's this VAX exec bit?  
>> Perhaps in my imagination? I don't read about VAX arch and VMS internals 
>> sinde the early nineties, but I _think_ the entries in the page table 
>> have a protection mask allows marking a page as readable, but 
>> non-executable. I am wrong on that? Too many years, too much coffee and 
>> too many arch changes in my life... :(
> 
> well, i have this "vax11 780 hardware handbook" on my shelf, so i
> pulled it down and looked at it.  no mention of any execute-permission
> bit in there.
> 
> remember, the later pdp 11 models had i-space and d-space, but i never
> encountered anyone using them.  this was, of course, because the
> pdp-ll architecture made it really rather difficult: this may have put
> off the designers of the vax (for what i would consider irrational
> reasons -- the vax architecture would have been far more amenable to
> such a split).
> 
> of course, the design predated the morris worm, and back then there
> was far less emphasis on this sort of code cleanliness.  the
> industry's older and wiser now (even if some of its workers still rush
> around like rabid rabbits).

In later versions of RSTS programs could be linked with separate I & D space.
IIRC this doubled the address space available, and decreased the need for stuff 
like co-trees

-- 
Mike R.
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