PDP8

Any stories, collections or recollections of the earliest days of computers
or related projects
Martin
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Joined: 16 Feb 2018, 14:11
Location: Warwickshire

Re: PDP8

Post by Martin »

On another forum I visit, the (older) regulars are talking about punch card and paper tape reader/writers.

One guy was discussing the merits of paper tape versus the newer-fangled mylar tape (still punched holes - not magnetic tape). He said the mylar tape was thinner so you got more capacity on the same size reel, but if it escaped from the spools or boxes that were supposed to catch it, the resulting nightmare tangle was much worse than you ever got with paper tape.

Also the mylar tape was harder on the punches that made the holes, so they used to alternate mylar tape runs with ones using oiled paper tapes.

He worked for the military, and the little "chad" holes that the punches produced had to be collected and burned, because the top brass believed that if the bad guys got hold of the chad from the bins they would somehow be able to glean secrets about the code his organization was running! :lol: He said he tried arguing with them that the bins full of tiny punched-out circles couldn't conceivably carry any useful information - but they wouldn't listen.
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Igull
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Joined: 16 Feb 2018, 21:11

Re: PDP8

Post by Igull »

Martin wrote: 06 Jan 2019, 21:47 He worked for the military, and the little "chad" holes that the punches produced had to be collected and burned, because the top brass believed that if the bad guys got hold of the chad from the bins they would somehow be able to glean secrets about the code his organization was running! :lol: He said he tried arguing with them that the bins full of tiny punched-out circles couldn't conceivably carry any useful information - but they wouldn't listen.
I rest my military attaché case :D

The mylar chad in our place used to be deposited in the coat pockets of anyone having a birthday - or a bad day :lol: That and a well charged high-voltage capacitor thrown in their direction - wonder when health and safety started ????

Neil
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RON
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Location: Stokesley North Yorkshire

Re: PDP8

Post by RON »

Igull wrote: 07 Jan 2019, 21:27 That and a well charged high-voltage capacitor thrown in their direction - wonder when health and safety started ????

Neil
I remember once passing a mate a hammer thru screwdriver to remove the EHT cap of a colour CRT :D

I can still see the flash

Ron.
G0MBV Class A Radio Amateur, North Yorkshire
jackdaw
Posts: 165
Joined: 16 Feb 2018, 20:30
Location: Wet and Windy North Wales

Re: PDP8

Post by jackdaw »

I'm definitely on a different wavelength to the rest of you guys. When I saw the title I immediately thought it was about model engines, Super Tigre, with the Perry Directional Porting
Pchristy
Posts: 413
Joined: 16 Feb 2018, 13:57
Location: South Devon, UK

Re: PDP8

Post by Pchristy »

The very first computer I had "hands on" experience with was a PDP-8, running FOCAL - a sort of BASIC for doing calculations.

We also had an IBM mainframe, but programming that consisted of leaving a Fortran IV programming sheet in an in tray, waiting for the girls in the office to convert it to punched cards, and then a few days later, collecting the results in an out tray! Not very involving! And the out tray usually contained reams of paper marked in red saying "Run terminated, stuck in loop!"

At the time, my girl friend (now my wife) used to do the punch cards for a local business who ran an ICL machine for their accounts, so quite often, I could short circuit the system by providing ready punched cards! Not that that improved my programming skills much.... :(

But the PDP-8 was "hands on"! Ours had the 4K memory expansion - another box about the same size as the processor box, as the memory was all ferrite cores! We had three teletypes hooked up to it, each with access to 1K of RAM! Programs were stored on punched tape - still have a box of them somewhere, but I'd need FOCAL as well to run them!

FOCAL had a trace function. To run a program, you typed in GO, and to do a trace it was GO? ! If someone on a teletype tried to do a trace, it slowed all the other teletypes down to a crawl, with frustrated users thumping them, cursing and swearing, and wondering what was going on!

Oh, the fun we had running "Moon Lander" programs on them......! :lol:

--
Pete
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Igull
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Joined: 16 Feb 2018, 21:11

Re: PDP8

Post by Igull »

Pchristy wrote: 10 Jan 2019, 16:26 The very first computer I had "hands on" experience with was a PDP-8, running FOCAL - a sort of BASIC for doing calculations.
That was the basic - amazing how your mind gets rejuvenated for 10mS when you see someone else's comment :-)
We also had an IBM mainframe, but programming that consisted of leaving a Fortran IV programming sheet in an in tray, waiting for the girls in the office to convert it to punched cards, and then a few days later, collecting the results in an out tray! Not very involving! And the out tray usually contained reams of paper marked in red saying "Run terminated, stuck in loop!"
LOL, at least we could DIY the cards :-)
At the time, my girl friend (now my wife) used to do the punch cards for a local business who ran an ICL machine for their accounts, so quite often, I could short circuit the system by providing ready punched cards! Not that that improved my programming skills much.... :(
My accounts are still done by punched card I think.
But the PDP-8 was "hands on"! Ours had the 4K memory expansion - another box about the same size as the processor box, as the memory was all ferrite cores! We had three teletypes hooked up to it, each with access to 1K of RAM! Programs were stored on punched tape - still have a box of them somewhere, but I'd need FOCAL as well to run them!
I can rememeber the production line ladies building ferrite core memories for Marconi 920b computers - work of art really.
FOCAL had a trace function. To run a program, you typed in GO, and to do a trace it was GO? ! If someone on a teletype tried to do a trace, it slowed all the other teletypes down to a crawl, with frustrated users thumping them, cursing and swearing, and wondering what was going on!
Oh, the fun we had running "Moon Lander" programs on them......! :lol:
As I recollect, it was 'flight of the bumblebee' from papertape on ours.

Unbelievable that today we can have a high speed 1Tb SD card for 4K video - far removed from even the 16Kb Sinclair rampack variety LOL.

Neil
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