A new fossil record

Ken Roach said:

The customer has no plans to replace this controller or upgrade it; they plan to run every machine in the place to failure.

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Ken did you come to our plant when I wasn't there? This sounds like the old plant engineer. Why fix it in won't break or will it?

Hey I was feeling pretty smug till Mike L. brought up the Idec FA2s. Suddenly I feel the age. I still have a soft spot for the old Idecs. Thanks Guys

RMA said:

The 8A, if I remember corrrectly was actually the last of the 19" rack PDP 8s, must have been mid to late '70s.

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I encountered them in '83. The place I worked at while working my way through school had three 8-A units. No one there knew anything about them and I saw an opportunity and took it upon myself to learn what I could about programming and maintaining them. They were reliable but when they went down they could really tax my patience. They were power hogs too, those units were in air conditioned racks.

'83 was late enough that we had an Apple II so that we could enter the programs into a text editor and then punch a paper tape, so I only keyed in a boot routine and then loaded the rest with the punch tape, so the keypad was never much of an issue. Just one year later the world was very different, but those 8As were still in operation into the mid 90's.

robertmee said:

We ran an entire plant on PDP11's and uVaxes. Fun days

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I'm not sure I would go straight to fun. I remember a lot of frustration. Sometimes it was a bit of a challenge to work with the limited instruction set. Thats the era that produced many of the bit twiddling hacks that surface from time to time in threads here.

Quote:
Originally Posted by robertmee
We ran an entire plant on PDP11's and uVaxes. Fun days

I'm not sure I would go straight to fun. I remember a lot of frustration. Sometimes it was a bit of a challenge to work with the limited instruction set.

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I'm with Robert on this one. Because I only worked with the PDP8 for a couple of years before moving on to the PDP11, I had to look up the instruction set to remind myself what it was like, but the PDP11 was a completely different kettle of fish, instruction-wise it was effectively a scaled down mainframe, fun is definitely the right word here! I left the company about the time they started considering implementing the VAX and only worked with VAXes in an IT environment. I do remember dreaming of having a Micro-VAX at home, though!

You're right about the side-effects of the restricted instruction set and memory space, though. The lead programmer when I joined the company in 1969 had the reputation of writing perfect programs straight off that didn't need any debugging. Whether that was true is irrelevant, but the guy was a genius when it came to writing efficient, compact code. The not insignificant side-effect was that nobody else could understand or maintain the code!. Unfortunately the company promoted him to Software manager a few years later, which turned out to be a minor catastrophe - his estimates of programming time required were usually off by at least 100%!

What I remember is that the PDP-8 used a three bit opcode. If I recall correctly op codes 000 thru 110 performed operations on the value in the accumulator and the value at the addressed memory word. Op code 111 operated on only the ACC so you could use the other bits to specify what operation to do on the accumulator allowing you to clear bits and shift or rotate bits, so in this way it provided a limited extension to available instructions. Its been a while so I don't remember all of what they were. I do remember that the only math instruction available was an add instruction, so subtraction required that you first convert one value to twos compliment and then add, not difficult, just a PITA to have to do it all yourself one step at a time. Just loading a value into the accumulator was a three step process - first you cleared the accumulator. Then you cleared the carry bit. Then you added the value in a memory address to the value of 0 in the accumulator. At times the PDP-8A challenged me in some very vexing ways, I was still a student, but it was fun when a problem was solved - I just remember that it included at least as much frustration as fun. However, it was my experience with the PDP-8A that steered me into controls because it was still satisfying to see the machinery it was controlling come to life and do what it was supposed to do.

I never had a chance to work with the PDP-11. It might have been a different experience. Later on I moved on to using an 8088 processor based embedded controller that I programmed in C (the first control system I wrote from scratch) - and that was fun. I encountered my first PLC around '85.

The old ferrite core memory fascinated me. It still does. Did you know everyone of those cores was handwired? No one ever invented a machine that could wire them.

I still have an automatic weighing sortation system that uses the 8086 processor everything on this system is TTL except the relays to the kickers. I still remeber programming with the instruction set and the math restrictions took some interesting thought as to how to perform certain math functions.

rguimond said:

We just took out our last Tenor Stepper last year. Used to open/close valves during CIP.

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Where was this? I worked at a process company. WHE Process Systems, that in the 80s installed the Tenor for CIP in almost all dairy plants in Southern Ontario and parts of Quebec.

PeterW said:

That was the only PLC I've ever used that could use the same Timer as many times as you like, saving and restoring the individual time base and accumulated values.

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Which was necessary because IIRC there were only 64 timer addresses available.

Just think....

someday there will be a thread similar to this one, except it'll go something like this:


Back in the day we had to program ControlLogix plcs and can you believe it, we had to use Windows based software and our program was saved on a magnetic hard disk and we had to load the programs using an actual cable....

curlyandshemp said:

Where was this? I worked at a process company. WHE Process Systems, that in the 80s installed the Tenor for CIP in almost all dairy plants in Southern Ontario and parts of Quebec.

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I was working at the dairy in Copper Cliff recently. They have a stepper there that is still in operation.
Must admit my jaw dropped when I saw it.

bernie_carlton said:

I'm waiting for: "I had to repair a Jacquard Loom the other day ..."

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leitmotif said:

Did any of you guys put in the propulsion control systems on Roman galleys??

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Haha... no kidding. I suddenly feel very young when I hear some of you talking about working on systems that existed a decade before I was born.

New Brunswick.

I really liked the Tenor - easy to visualize what was supposed to happen. Much nicer than running a sequencer.

Too bad the motors in the Tenors were so terrible.

We have video of Vice-President Lyndon Johnson visiting a control room ~1960 to congratulate the new Titan engine for an ICBM (later used in Gemini flights). The control room looks almost the same, with manual switches on large panels, and they tested that way until deactivated recently. Upgrades were Durant timers then an HP21MX computer, still used in other control rooms.

The worker's wives marched outside in beehive hairdos with signs saying, "we closed the (missile) gap, don't close the plant". A year later, employment dropped from >20,000 to <2000 and you could buy a house for a dollar.

We still have some idec micro 1`s running! i still carry the small hand loader in my brief case lol. You program in boolean.
I`ve worked on lift stations that were hard wired using relays, rachit relays, & pnuematic timers and used a plc to control the fans and warning lights. I guess they didn`t trust the plc to control the pump motors? Some of you young ones would`ve loved to trouble shoot a chippin saw before plc`s ! All hard wired before triacs . Actually used a brush riding on a segmented cooper strip. This made up the veriable part of a wheatstone bridge. Used this to gauge the diameter of the incoming logs. Forgot how they determined length some kind of pulse from a distrutor of a car i believe. Dekota cylinders on the chipping heads and twin band saws . It all worked, but you could only run logs about 150 fpm no variable speed on feed. Anyone else work on these? They were made by cancar in canada.