Not to mention the absolutely wonderful "rope memory" used in the Apollo Guidance Computer systems. A form of almost physically indestructible ROM in which the memory contents were encoded (literally "hard-wired") by weaving (by hand) the sensor wires in and out of a string of ferrite cores.
Changing the contents of the memory meant unravelling the string and re-weaving the wires.
Sperry Univac had a drum memory that was ~6 feet in diameter and ~18 inchs wide. Had a head per track so no moving parts except the drum. Because of the large diameter it did not have to rotate very fast to get a high speed at the R/W head
hmmm. in the mid 80ies there was a type of Intel memory that acted as SRAM, but upon power failure was able to write the whole array into EEPROM or Flash cells, in parallel, before power was gone. don't remember the name though...
I actually "touched" magnetic core memory in the late 80's in a professional capacity. It was used in some Allan Bradley PLCs that were in an industrial plant I worked in as a student engineer. Hard to believe it was still in use as little as 25 years ago in functioning equipment.
This was really interesting. Good work. I'm dubious of one stat, though: it doesn't seem possible that the magnetic drum rotated at 750,000 rotations per second. In fact, that most definitely can't be true.
Sometimes in my HDL code when I use a delay line or Johnson ring I call it a mercury line. It's the same concept. The springs in old reverb units are similar--they're basically FIFOs.
In addition to the magnetic core implementation shown, there were other variations according to the number of wires through each core. There were 2, 3, 4, and 5 wire varieties. In the 2-wire type, all the bits in a row are accessed at the same time. The Control Data Star-100 used this type of memory.
NASA's Orion Flight Software Production Systems Manager Darrel G. Raines joins Planet Analog Editor Steve Taranovich and Embedded.com Editor Max Maxfield to talk about embedded flight software used in Orion Spacecraft, part of NASA's Mars mission. Live radio show and live chat. Get your questions ready.
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