core memory
in [Design]
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From: Baron on 5 Dec 2009 16:18 John Larkin wrote: > Testing some FTP stuff, threw up some test files... > > ftp://jjlarkin.lmi.net/Core_304bits.jpg Why 19x16 bits ? > ftp://jjlarkin.lmi.net/Core_4K.jpg > > ftp://jjlarkin.lmi.net/Core_4Kdetail.jpg > > John Nice pics. -- Best Regards: Baron.
From: Joerg on 5 Dec 2009 16:33 John Larkin wrote: > 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 > 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. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: John Larkin on 5 Dec 2009 17:05 On Sat, 05 Dec 2009 13:33:53 -0800, Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: >> 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 >> > >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. 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
From: John Larkin on 5 Dec 2009 17:09 On Sat, 05 Dec 2009 19:03:54 GMT, Jan Panteltje <pNaonStpealmtje(a)yahoo.com> wrote: >On a sunny day (Sat, 05 Dec 2009 10:51:36 -0800) it happened John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in ><kqalh59i8jsogn1t6p3ghuaop5c137qtoj(a)4ax.com>: > >>Testing some FTP stuff, threw up some test files... >> >>ftp://jjlarkin.lmi.net/Core_304bits.jpg > >16 bits x 19?? > > >>ftp://jjlarkin.lmi.net/Core_4K.jpg > >Amazing.. > > >>ftp://jjlarkin.lmi.net/Core_4Kdetail.jpg > >Must have been expensive. > > >>John >> >> >> I remember when IBM announced that they had reduced the price of mainframe core to below $50,000 per megabyte. I was very young at the time, of course. John
From: artie on 5 Dec 2009 17:21
In article <L6ASm.76416$Pi.70738(a)newsfe30.ams2>, Andrew Holme <ah(a)nospam.co.uk> wrote: > "ChrisQ" <meru(a)devnull.com> wrote in message > news:qmySm.123940$yM2.60574(a)newsfe10.ams2... > > Jan Panteltje wrote: > >> On a sunny day (Sat, 05 Dec 2009 10:51:36 -0800) it happened John Larkin > >> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in > >> <kqalh59i8jsogn1t6p3ghuaop5c137qtoj(a)4ax.com>: > >> > >>> Testing some FTP stuff, threw up some test files... > >>> > >>> ftp://jjlarkin.lmi.net/Core_304bits.jpg > >> > >> 16 bits x 19?? > >> > >> > >>> ftp://jjlarkin.lmi.net/Core_4K.jpg > >> > >> Amazing.. > >> > >> > >>> ftp://jjlarkin.lmi.net/Core_4Kdetail.jpg > >> > >> Must have been expensive. > >> > >> > >>> John > >>> > >>> > >>> > > > > 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 > > 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: > > http://www.holmea.demon.co.uk/Core/Flipper.htm > 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! -- |