On Tuesday 04 May 2004 20:16, Jeff Vian wrote: >jludwig wrote: >>Keith corrected me on this which is ok since I had an Old (brain) >> fart! It's nice to see someone who knows or remembers, and I find >> this reminder very interesting and educational. >> >>On Mon, 2004-05-03 at 19:23, Keith Lofstrom wrote: >>>You wrote: >>>>For those who don't know what core memory is, it's miniature >>>> ferrite beads strung together with three wires through them to >>>> read/write [magnetize and demagnetize], and reset if I remember >>>> correctly. I have seen 16 MB of core memory, it was the size of >>>> a full size tower case. >>> >>>Some corrections of fact, which I will share with you privately. >>>You can research and post; it is always better to correct >>> yourself than have someone else do it publically. >>> >>>The three wires in a core memory are X select, Y select, and >>> sense. The cores work by pushing an X current and a Y current >>> through an intersection; two currents pushed the hysteretic >>> toroidal magnetic core past a threshold, either causing it to >>> flip magnetic polarity (generating a little voltage blip on the >>> sense line) or not, depending on previous magnetization. After >>> flipping a core during a read, you had to schedule a reverse set >>> of currents on the same X and Y wires to put the core back. The >>> size of the arrays were limited by the number of cores you could >>> put on a sense wire before accumulated noise made reading >>> unreliable. >>> >>>A friend in high school wanted to build a core memory, and wrote a >>> letter to Honeywell. They sent him a one pound jar of 15mil >>> cores. All out of spec, as near as we could measure. >>> >>>What you probably saw was a 16*K* byte memory, the boards from the >>> late 60s were typically around 16K bits, 8 boards to a byte, and >>> about as big on a side as a tower case with the small scale >>> integration driver chips around the sides of the core fabric. A >>> 16MB machine would have been gargantuan, indeed; I would guess >>> 100 or more 19inch racks, 8 feet tall, and probably costing on >>> the order of $50M in current dollars. >>> >>>Keith > >yeah, things were big and expensive. >In 1990 the military base where I was stationed finally upgraded the > IBM mainframe they used to 64 mb memory. They had been running on > 16 mb and that was almost impossible to get approval for the > expense. > >And in one PC we needed more drive space. A 400MB hard drive was > $1600. Now we cannot even load an OS on a drive that size. Uh huh, and a 40Gb drive is now $62 at tcwo. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) 99.22% setiathome rank, not too shabby for a WV hillbilly Yahoo.com attorneys please note, additions to this message by Gene Heskett are: Copyright 2004 by Maurice Eugene Heskett, all rights reserved.
