PDP-11 Still Working In Nuclear Plants - For 37 More Years

Taco Cowboy writes "Most of the younger /. readers never heard of the PDP-11, while we geezers have to retrieve bits and pieces of our affairs with PDP-11 from the vast warehouse inside our memory lanes." From the article: "HP might have nuked OpenVMS, but its parent, PDP-11, is still spry and powering GE nuclear power-plant robots and will do for another 37 years. That's right: PDP-11 assembler programmers are hard to find, but the nuclear industry is planning on keeping them until 2050 — long enough for a couple of generations of programmers to come and go." Not sure about the OpenVMS vs PDP comparison, but it's still amusing that a PDP might outlast all of the VAX machines.

Comments

I cut my teeth on that CPU

[Bucc5062]

The PDP-11/45 was the very first computer I ever worked with at College in 1978. God I hate to sound like an old guy with a lawn, but they just don't make like that any more. I learned RATFOR, Pascal, c, and Assembler during that time. Even later on, thanks to my time on the PDP11 I expanded system knowledge working with the HP1000 and its front panel switches.

Good times....good times.

Re:I cut my teeth on that CPU

[Anonymous Coward]

Many of us still can program in macro-11. I got tired of ODT though and built a symbolic debugger with DDT that ran in another task.

The pdp11 has a number of possible hacks that can be useful in remotely identifying code. Ever try a DIV on SP, which moves the stack and changes
the program counter all at a go? Mov @offset(r5),pc ? That gives control transfer an extra level of indirection. There are others.
Note the DIV hack works only for CPU models with the EIS instructions.

The pdp11/45 has a 300 ns. cycle time though, corresponding to ~3.3MHz clock speed. Current machines have more like ~3.3GHz.
The larger 11s could address 4MB of memory (a lot in those days). Now a 4GB machine is beginning to look small.
I recall when we got a 22MB hard drive (size and shape of a clothes washing machine; we put Dymo labels under the lights
labelled "wash rinse dry" for fun) it seemed vast. Nowadays it is not unheard of for a home machine to have 22TB.

With all those factors modern machines can be said to have grown by a factor of maybe a trillion.

Still the pdp11 was versatile and allows significant and useful code to run. It is usually programmed in assembler (macro11;
nobody uses PAL11R any more I hope) or Fortran or C. (The original pdp11 Fortran was a nightmare of code inefficiency, could
burn 100 instructions to add 2 integers where the hardware could do it in one. Only the later f4p compiler got half decent code
generation.)

I only ever saw mov -(pc),-(pc) used as a fast clear memory; it traps at the end, but won't get any unmapped addresses.

It was more fun to arrange to handle interrupts in supervisor mode. (Did that too. Needs a lil trick to RTI.)

Re:I cut my teeth on that CPU

[Giant Electronic Bra]

Yeah, I know what you mean. A lot of newer technology is just less good. Verizon 'improved' my phone service so now they 'back up' my contact list. Its great, every month or so they restore some old worthless crap over the top of my contact list on my phone. Ain't progress great? Now I carry around an actual physical address book.