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What Have We Learned from the PDP-11?

149 点作者 davecheney超过 7 年前

16 条评论

simulate超过 7 年前
We had a terminal to a PDP-11 70 in our middle school library in 1977 when I was 12. The terminal printed on green and white striped paper and no one at our school knew how to operate it until a friend and I began to play with it. I hand-typed games from this book: <a href="https:&#x2F;&#x2F;www.atariarchives.org&#x2F;basicgames&#x2F;showpage.php?page=cover-digital" rel="nofollow">https:&#x2F;&#x2F;www.atariarchives.org&#x2F;basicgames&#x2F;showpage.php?page=c...</a><p>which eventually led to me writing my own programs.<p>The actual PDP 11 was located at a local college. After learning a bit more about the architecture, we two twelve-year-olds called the administrator and asked for root privileges. Sadly, he said, &quot;No.&quot; :-)
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panic超过 7 年前
<i>One can write a string copy routine using two instructions, assuming that the source and destination are already in registers.</i><p><pre><code> loop: MOVB (src)+, (dst)+ BNE loop </code></pre> Suddenly the C idiom<p><pre><code> while (*dst++ = *src++); </code></pre> makes a lot more sense!
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oldgradstudent超过 7 年前
The Technion in Israel still teaches PDP-11 assembly language in its computer organization course -- using an simulator, of course.<p>It&#x27;s a nice, simple, orthogonal instruction set. The textbooks are available. Why change? Here&#x27;s the syllabus of the latest incarnation: <a href="https:&#x2F;&#x2F;webcourse.cs.technion.ac.il&#x2F;234118&#x2F;Spring2017&#x2F;syllabus.html" rel="nofollow">https:&#x2F;&#x2F;webcourse.cs.technion.ac.il&#x2F;234118&#x2F;Spring2017&#x2F;syllab...</a>
dboreham超过 7 年前
His book &quot;Computer Engineering&quot; is an interesting read. I noticed someone posted a scan PDF : <a href="http:&#x2F;&#x2F;bitsavers.trailing-edge.com&#x2F;pdf&#x2F;dec&#x2F;_Books&#x2F;Bell-ComputerEngineering.pdf" rel="nofollow">http:&#x2F;&#x2F;bitsavers.trailing-edge.com&#x2F;pdf&#x2F;dec&#x2F;_Books&#x2F;Bell-Compu...</a><p>I have a copy of the book. And a PDP-11. Well, most of one, in a closet.
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Animats超过 7 年前
<i>4096 word memory contained 16 million cores</i><p>No, no. 4096*16 = 65536 bits.<p>16 million cores would be 2 megabytes. An IBM mainframe of the early 1970s might have that much storage, and the cost would be about $1 million. IBM figured out how to weave core memory on a power loom, which gave them a big cost advantage for a while.
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digi_owl超过 7 年前
It seems that all successful computer designs, large or small, have one thing in common. the presence of a expansion system that allow the computer to take on different tasks for different users.<p>UNIBUS, S100, ISA, AppleII expansion slots, etc etc etc.
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timonoko超过 7 年前
I had PDP-11 for my personal use in the Finnish Army in 1978. It was quite useless and I learned nothing: <a href="https:&#x2F;&#x2F;www.flickr.com&#x2F;photos&#x2F;timonoko&#x2F;27931368650&#x2F;in&#x2F;album-72057594100241331&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.flickr.com&#x2F;photos&#x2F;timonoko&#x2F;27931368650&#x2F;in&#x2F;album-...</a>
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peterburkimsher超过 7 年前
My dad started on a PDP-8 at my granddad&#x27;s workplace (a newspaper).<p>He later wrote his PhD thesis on an Epson HX-20 and backed it up to PDP-11 magnetic tape.<p>When I was 16, we went to a computer museum to try to get his old backup off, but their PDP-11&#x27;s Winchester hard drive was broken, so we couldn&#x27;t boot it to load up something to read the tape.<p>Lesson to learn: copy your old backups forward when storage formats change.
cyberferret超过 7 年前
Wow - one of my first jobs in computing was changing the backup disks (huge things - bigger than an LP record) on an old Vax PDP-8 and PDP-11 system in my boss&#x27;s parents business.<p>Mounting and dismounting those things was one of the factors that made me swear I would get more into the software side of these new fandangled &#x27;computer&#x27; thingies rather than hardware... :)
tasty_freeze超过 7 年前
You can easily see the influence of the PDP-11 on the 68000 architecture and instruction set.
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flyinghamster超过 7 年前
Overall, a very good article, though I&#x27;d pick this nit: separate I&#x2F;O instructions survive in 8086 and AMD64 as well, at the very least.<p>Never having done ARM assembly language programming, does ARM have I&#x2F;O instructions, or is it strictly memory-mapped?
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thechao超过 7 年前
For those of you recalling fond memories of PDP days, just remember the poor wretches still using these devices. Thankfully, this is no longer me.
fuzzfactor超过 7 年前
&gt;through the lens of our own 20&#x2F;20 hindsight<p>Here&#x27;s another quote from the article that seems to be a constant feature over the decades:<p>&gt;PDP is an acronym for “Programmed Data Processor”, as at the time, computers had a reputation of being large, complicated, and expensive machines, and DEC’s venture capitalists would not support them if they built a “computer”<p>Looks like some VC&#x27;s have always been more impressed by the slide deck and presentation than the actual potential of the business concept or individuals developing the technology.<p>That&#x27;s something worth learning as well.<p>Anyway, anybody want a used VAX 4000-200? Available for pick up in Houston this week.<p>If so, post PM info here along with what you would like to do with it.<p>I&#x27;ll check this thread in a few days to see if there is any interest.<p>Also, an HP1000 in a full rolling rack the size of a refrigerator.
OliverJones超过 7 年前
Blast from past! Too much time spent on that 11&#x2F;70&#x27;s front panel switches.<p>One thing I believe Bell missed in &quot;what we learned.&quot; Of course, maybe it&#x27;s hindsight. The regular instruction set in the &#x27;11 and the VAX was fertile ground for all sorts of innovation in compilers and optimization technology. Without those innovations it would have been harder for the gnarly-instruction processors (386 line, I&#x27;m looking at you) to gain users.
baking超过 7 年前
Regarding the UNIBUS, this needs a picture of the wire-wrapped backplane of a PDP-8 (especially the denser later versions with the flip-chips.) The front looks neat and tidy, but opening the back is still a part of my nightmares.
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leed25d超过 7 年前
I began programming as a career in 1974 after graduating from college. At the time, and well into the 90s, the PDP-11&#x2F;VAX was my favorite minicomputer.