core memory

Testing some FTP stuff, threw up some test files...

ftp://jjlarkin.lmi.net/Core_304bits.jpg

ftp://jjlarkin.lmi.net/Core_4K.jpg

ftp://jjlarkin.lmi.net/Core_4Kdetail.jpg

John

Reply to
John Larkin
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On a sunny day (Sat, 05 Dec 2009 10:51:36 -0800) it happened John Larkin wrote in :

16 bits x 19??

Amazing..

Must have been expensive.

Reply to
Jan Panteltje

Don't recognise either of those as to manufacturer, but the last machine that I had with core was an early pdp11/05, which eventually got shipped back to the us.

Ok, quiz time: how does core memory work ?. (and no cheating via google etc :-)...

Regards,

Chris

Reply to
ChrisQ

On a sunny day (Sat, 05 Dec 2009 19:18:45 +0000) it happened ChrisQ wrote in :

OK, without cheating, I have never used core memory so... XY wires, magnetize one core at X,Y. There is also a read wire, mabe use a lower power to address the one you want to read, and then the read wire will give a signal depending on the magnetisation of that specific core.. Or maybe use full power to address, and then write back a 1 if it was a 1, and a 0 if it was a 0, so opposite magenetisation for 0 and 1. Not sure. Something like that. Am watching a weid kung fu movie, so ...

Reply to
Jan Panteltje

The cores have hysteresis. You can't flip the direction of magnetisation unless the current in the wires exceeds a certain threshold. You put half the required current down an X wire and half down a Y wire. Only one core at the X,Y intersection gets flipped.

When you flip a core, you get a pulse induced in the read wire. This means you have to do a destructive read. If you write a 1 and get a big pulse back then you know it must have been a 0 before. If it was already a 1, you only get a tiny pulse. Every read must be followed by a write to restore the previous state.

See my core memory page for 'scope captures of actual read pulses:

formatting link

Reply to
Andrew Holme

Why 19x16 bits ?

Nice pics.

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Best Regards:
                     Baron.
Reply to
Baron

Here I must confess that I cruelly re-purposed some of those. People made matrix keyboards with them because the hysteresis provided an easy way to avoid contact bounce (you had to reset the cores before the next keystroke was accepted). So, snip, snip, snip, clicker, clicker, into a bag and gave them away. Back in the 70's keyboards with German layout were very expensive, some had odd interfaces, and buying 30-40 push button switches was a lot cheaper. You could buy them with a step and then glue a label onto the lower step. I think they still make them.

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Regards, Joerg

http://www.analogconsultants.com/
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Reply to
Joerg

There were some jukeboxes that used core memory - BIG cores, one per record - to remember which records had been selected/paid for to play.

John

Reply to
John Larkin

I remember when IBM announced that they had reduced the price of mainframe core to below $50,000 per megabyte. I was very young at the time, of course.

John

Reply to
John Larkin

You usually drove more like 0.6 or so of the required current through both X and Y, just to make sure... Also, you had to keep the cores at a steady operating temperature, which usually meant heating the enclosure, or pushing warm air through the memory bays at a known temperature.

Most core planes had one sense line per plane; some had more. The sense line is where you (hopefully) sensed the tiny pulse on the read side that said you'd flipped a bit.

A good friend back in those mainframe days that taught hardware CEs used to pull sense amp boards, use a solder sucker to remove all the solder from the sense amp input pins, and then after unplugging his soldering iron, made the crummiest, coldest connection possible not really reconnecting the sense amp pin to the trace on the PCB. Then he'd spend an inordinate amount of time with emery boards and such polishing up the connection so it looked all shiny and bright! Swap out a good sense amp board with one of those, and you were in for a load of fun!

Roy, wherever you are, I wish you well!

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Reply to
artie

On a sunny day (Sat, 5 Dec 2009 21:18:35 -0000) it happened "Andrew Holme" wrote in :

Cool!

Reply to
Jan Panteltje

More likely 16 words x 18bit+parity. Apparently some control store of some sequencer.

That is just a bit plane.

Apparently not, since core memory was used until the introduction of

16 Kid DRAM chips.

Intel even used 8 Kid (partially faulty 16 Kid) chips to allow the physical PDP-11 memory expansion to the huge 4 MiD. Due to the bus length limitations, only 1 MiD could be used with core, while the semiconductor memory allowed the full 4 MiD to be used.

Reply to
Paul Keinanen

I vaguely remember a nuke simulator that used cores about 1" in diameter.

Best regards, Spehro Pefhany

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"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
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Reply to
Spehro Pefhany

I recall that an additional 4Kx16 core for a PDP-11/20 was about $4000.

John

Reply to
John Larkin

Cheapest core ever got was a nickel a bit, less drivers and read circuitry.

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Many thanks,

Don Lancaster                          voice phone: (928)428-4073
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Reply to
Don Lancaster

I still have a PDP 11/05 core unit hanging on my wall along witg a disk platter and a few other things from that machine.

Reply to
PeterD

That must have been semiconductor memory.

Reply to
krw

...and weren't embarrassed to collect twice for the same tune.

Reply to
krw

Exactly. But if some yahoo pulled the plug out of the wall, as they were wont to do, and it was replaced, the request wasn't lost.

John

Reply to
John Larkin

Can't be government because it is not Air Corps..

Reply to
Robert Baer

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