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: https://www.atariarchives.org/basicgames/showpage.php?page=c...
which eventually led to me writing my own programs.
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, "No." :-)
One can write a string copy routine using two instructions, assuming that the source and destination are already in registers.
Suddenly the C idiom
loop: MOVB (src)+, (dst)+ BNE loop
makes a lot more sense!
while (*dst++ = *src++);
The Technion in Israel still teaches PDP-11 assembly language in its computer organization course -- using an simulator, of course.
It's a nice, simple, orthogonal instruction set. The textbooks are available. Why change? Here's the syllabus of the latest incarnation: https://webcourse.cs.technion.ac.il/234118/Spring2017/syllab...
His book "Computer Engineering" is an interesting read. I noticed someone posted a scan PDF : http://bitsavers.trailing-edge.com/pdf/dec/_Books/Bell-Compu...
I have a copy of the book. And a PDP-11. Well, most of one, in a closet.
4096 word memory contained 16 million cores
No, no. 4096*16 = 65536 bits.
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.
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.
UNIBUS, S100, ISA, AppleII expansion slots, etc etc etc.
I had PDP-11 for my personal use in the Finnish Army in 1978. It was quite useless and I learned nothing: https://www.flickr.com/photos/timonoko/27931368650/in/album-...
My dad started on a PDP-8 at my granddad's workplace (a newspaper).
He later wrote his PhD thesis on an Epson HX-20 and backed it up to PDP-11 magnetic tape.
When I was 16, we went to a computer museum to try to get his old backup off, but their PDP-11's Winchester hard drive was broken, so we couldn't boot it to load up something to read the tape.
Lesson to learn: copy your old backups forward when storage formats change.
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's parents business.
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 'computer' thingies rather than hardware... :)
You can easily see the influence of the PDP-11 on the 68000 architecture and instruction set.
Overall, a very good article, though I'd pick this nit: separate I/O instructions survive in 8086 and AMD64 as well, at the very least.
Never having done ARM assembly language programming, does ARM have I/O instructions, or is it strictly memory-mapped?
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.
>through the lens of our own 20/20 hindsight
Here's another quote from the article that seems to be a constant feature over the decades:
>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”
Looks like some VC'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.
That's something worth learning as well.
Anyway, anybody want a used VAX 4000-200? Available for pick up in Houston this week.
If so, post PM info here along with what you would like to do with it.
I'll check this thread in a few days to see if there is any interest.
Also, an HP1000 in a full rolling rack the size of a refrigerator.
Blast from past! Too much time spent on that 11/70's front panel switches.
One thing I believe Bell missed in "what we learned." Of course, maybe it's hindsight. The regular instruction set in the '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'm looking at you) to gain users.
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.
I began programming as a career in 1974 after graduating from college. At the time, and well into the 90s, the PDP-11/VAX was my favorite minicomputer.