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anecdotes:a.out_percolate

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anecdotes:a.out_percolate [2016/01/12 10:30]
wkt created
anecdotes:a.out_percolate [2016/01/12 10:34] (current)
wkt
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 Back around 1970-71, Unix on the PDP-11/20 ran on hardware that not only did not support virtual memory, but didn't support any kind of hardware memory mapping or protection, for example against writing over the kernel. This was a pain, because we were using the machine for multiple users. When anyone was working on a program, it was considered a courtesy to yell "​A.OUT?"​ before trying it, to warn others to save whatever they were editing. Back around 1970-71, Unix on the PDP-11/20 ran on hardware that not only did not support virtual memory, but didn't support any kind of hardware memory mapping or protection, for example against writing over the kernel. This was a pain, because we were using the machine for multiple users. When anyone was working on a program, it was considered a courtesy to yell "​A.OUT?"​ before trying it, to warn others to save whatever they were editing.
  
-[A substory: at some point several were sitting around working away. Bob Morris asked, almost conversationally,​ "what are the arguments to ld?" Someone told him. We continued typing for the next minute, as a thought began to percolate, not quite to the top of the brain-- in other words, not quite fast enough. The terminal stopped echoing before anyone could stop and say "Hold on Bob, what is it you're trying to do?"]+[A substory: at some point several were sitting around working away. Bob Morris asked, almost conversationally,​ "what are the arguments to **ld**?" Someone told him. We continued typing for the next minute, as a thought began to percolate, not quite to the top of the brain -- in other words, not quite fast enough. The terminal stopped echoing before anyone could stop and say "Hold on Bob, what is it you're trying to do?"]
  
 We knew the PDP-11/45, which did support memory mapping and protection for the kernel and other processes, was coming, but not instantly; in anticipation,​ we arranged with Digital Special Systems to buy a PDP-11/20 with KS-11 add-on. This was an extra system unit bolted to the processor that made it distinguish kernel from user mode, and provided a classical PDP-10 style "​hi-seg"​ "​low-seg"​ memory mapping unit. I seem to recall that maybe 6 of these had been made when we ordered it. We knew the PDP-11/45, which did support memory mapping and protection for the kernel and other processes, was coming, but not instantly; in anticipation,​ we arranged with Digital Special Systems to buy a PDP-11/20 with KS-11 add-on. This was an extra system unit bolted to the processor that made it distinguish kernel from user mode, and provided a classical PDP-10 style "​hi-seg"​ "​low-seg"​ memory mapping unit. I seem to recall that maybe 6 of these had been made when we ordered it.
anecdotes/a.out_percolate.txt ยท Last modified: 2016/01/12 10:34 by wkt