On Wed, 2004-10-27 at 15:09, Randall R Schulz wrote:
Darrell,
On Wednesday 27 October 2004 11:16, Darrell Cormier wrote:
...
Just curious if any of you have every worked with a machine that used core memory. If I remember correctly you basically had a cage of "boards". Each board was an x-y grid of fine wire and around each intersection of the wires was a ring of some ferrous oxide material. A current was applied to a certain x-y coordinate to charge the ring thus representing a binary 1. This was a system that had a destructive read which required you to write back what you just read.
I have never used one myself but one of my college instructors had one of these cages of core memory modules from a machine he had used in his youth. Quite interesting.
We had such a museum-piece in the Computer System Lab at the University of Wisconsin when I worked there in the late 70s and early 80s, but no computers that used it. The oldest computer we had was a PDP-11/20 equipped with a fixed-head hard drive, a card reader and a very low-resolution CRT monitor.
Core memory was interesting in a lot of ways. It was horribly slow by today's standards and likewise the density was abysmal by comparison with any kind of solid state RAM. Reading it destroys the stored memory, so the controller always had to write the value back. On the other hand, real core memory is non-volatile, so you could power the machine down and when you next turned it on, the contents of main store would be what they were when you shut it down.
Darrell C.
Randall Schulz
My old boss (this was circa '89-'90) had worked at IBM in the 60's when toroidal core memory -- hand sewn in India, btw -- was leased (not sold) to the Wall Street crowd for $250,000 a year per MB. He described having to duck his head while walking through the mass storage rooms with machinery whirring and media reels screaming past overhead on tracks. He said if you got hit with one of those things it'd plant you on the "far wall." Now you can't give a 1 MB SIMM away and you can barely squeeze your fingers into a pc case to do any work! Just my 2 cents on this one... regards, - Carl