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| Core Memory |
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| retrolefty:
--- Quote from: jimdeane on August 16, 2015, 11:54:55 pm ---Now for a mercury delay line memory... --- End quote --- I worked repairing video terminal equipment in the early 70s that used mechanical delay line for display memory. Just a flat disk of some kind of springy wire with transducers on the end points. It had like a 8 millisecond delay with 74xx logic to either insert new data or just recirculate output data back into input data point. Worked great and was very relaible, but very expensive for the number of bits it could recirculate per video frame. Worked on troubleshooting and repairing mini-computers core memory modules (mostly 8K x 16 or 16K x 16) at the same time. They also were very expensive with good reliability, bad sense amp ICs are about the only failures I saw at the time. Even back then most of the core memory mats were being hand-wound by females in Asia. |
| eneuro:
--- Quote from: @rt on August 25, 2015, 01:49:28 pm ---But I am interested in rectangular loop ferrite, I would like to follow on Jeri Ellsworth’s experiment with core logic. --- End quote --- Jeri "Circuit Girl" has 200k hits on YT on core memory so far, but why not to go to the origins? >:D Yep, made by U.S.A. military many years ago :-+ Electronics: Magnetic Cores I: Properties 1961 US Army Training Film Maybe, in spare time I will try make 1 bit core memory, just to see how long time it will keep holding this information without refreshing, etc >:D However, those days probably more interesting could be create qubits, but lets go back in time and play with core memory to warm up for quantum computing :popcorn: |
| @rt:
My 64 bit RAM has not failed as an EEPROM yet, unless I try to corrupt it with another magnet. To get it non-volatile I did have to turn off the micro’s power up delay to reset the shift registers as fast as possible, because otherwise, TI shift registers 74HC164/595 both like to start in a set state, and turn on all current drivers, and set cores before the program is even running. I have watched as many core RAM/Rope/Logic videos I can find including both of those several times. He seems to begin with general logic, and then focus on a shift register as an example. Finding the right ferrite might still stump me... I can hardly wind up to 12 or so turns around a 1mm core. |
| eneuro:
--- Quote from: @rt on August 26, 2015, 07:29:37 am ---I can hardly wind up to 12 or so turns around a 1mm core. --- End quote --- Which is inside diameter of those cores? Why not to use slightly bigger one since it is still 8 x 8 array I guess? I'll have in hands a lot of those FRH035050 Ferrocore ferrite beads which is 5mm long, outside diameter 3.5mm and internal 0.65mm. At least they specify core material as Ni-Zn, but probably its histeresis is bad for core memory. It looks like oryginal internal thick wire can be easy removed and custom thin windings inserted instead. However, I'd like to take advantage of toroid length to multiply its inductance while keeping outside diameter below 5mm, but this is specyfic to other low power tiny SMPS project, but I thought that maybe those ferrite bead Ni-Zn could be also usable in core memory experiment, but I've no datasheet how its histeresis might look like ??? Anyway, maybe did you experimened with demagnetization of those core memory toroids? I mean, maybe it is possible to store not only 0/1 bit for given saturated core flux direction, but... 3th state with very small residual magnetizm after demagnetization of core vere performed? ::) Is it possible to findout somehow that core memory was never set before to 0 or 1, so in theory we could have three core states with different residual magnetism (Brm): +Brm 0Brm -Brm Basicly, I'd like to know not only if core is in +/-B residual magnetism state after magnetization (0 or 1 bit set), but if it was ever magnetized (set to bnary 1 or 0) and not sure if is it possible read somehow this 3rd core memory state to detect this? :-// Do you use this single-diode transfer loop concept shown in video I've linked above to read/write core memory or different method? Trying to figureout howto check if core was magnetized, than when our read were it wasn't even if we used destructive method, we could perform demagnetization to "store" again this core state :-/O |
| @rt:
Hi :) Sorry for neglecting to check the thread. I will answer as best I can. Consider that I researched hard, but before this, in hindsight, didn’t know much about transformers, and didn’t understand at all the concept of pulse transformers. The cores I got quoted on eBay as 1mm cores, it turns out to be the outside diameter, but there isn’t much meat to them. You can definitely test hysteresis quality of a single core probably better than me, but I knew the particular ferrite due to the other two previous core RAM experiments. I got mine from the same eBay seller. Two people have done a successful experiment that I know, one a 32 bit RAM, and the other, a 1 bit RAM so far, but Wayne’s page does go into some more practical detail about testing one bit. You simply switch it’s state with a single current wire while looking at another scope channel at a sense wire. If you can alternate current direction along the current carrying wire, you can observe a pulse from the sense wire on the other channel if the state changed. Wayne has documented that well. There would be better ways to test the rectangle loop pattern, but if you can see a switch pulse then the core has some hysteresis quality. With regard to storing a third state.... Maybe if you could operate it faster than it could switch you might be able to demagnetise it, and sense a weaker pulse for the initial magnetisation. My understanding of the core and the hysteresis loop is they are truly bistable and would not store a partial state. Like a rubber band being pulled on until it breaks suddenly. If the core did not snap it’s direction very fast like a spring you would not receive the sense pulse, and there is a threshold where that occurs. --- Quote from: eneuro on August 26, 2015, 09:46:33 am --- --- Quote from: @rt on August 26, 2015, 07:29:37 am ---I can hardly wind up to 12 or so turns around a 1mm core. --- End quote --- Which is inside diameter of those cores? Why not to use slightly bigger one since it is still 8 x 8 array I guess? I'll have in hands a lot of those FRH035050 Ferrocore ferrite beads which is 5mm long, outside diameter 3.5mm and internal 0.65mm. At least they specify core material as Ni-Zn, but probably its histeresis is bad for core memory. It looks like oryginal internal thick wire can be easy removed and custom thin windings inserted instead. However, I'd like to take advantage of toroid length to multiply its inductance while keeping outside diameter below 5mm, but this is specyfic to other low power tiny SMPS project, but I thought that maybe those ferrite bead Ni-Zn could be also usable in core memory experiment, but I've no datasheet how its histeresis might look like ??? Anyway, maybe did you experimened with demagnetization of those core memory toroids? I mean, maybe it is possible to store not only 0/1 bit for given saturated core flux direction, but... 3th state with very small residual magnetizm after demagnetization of core vere performed? ::) Is it possible to findout somehow that core memory was never set before to 0 or 1, so in theory we could have three core states with different residual magnetism (Brm): +Brm 0Brm -Brm Basicly, I'd like to know not only if core is in +/-B residual magnetism state after magnetization (0 or 1 bit set), but if it was ever magnetized (set to bnary 1 or 0) and not sure if is it possible read somehow this 3rd core memory state to detect this? :-// Do you use this single-diode transfer loop concept shown in video I've linked above to read/write core memory or different method? Trying to figureout howto check if core was magnetized, than when our read were it wasn't even if we used destructive method, we could perform demagnetization to "store" again this core state :-/O --- End quote --- |
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