Sender: (Paul B. Schneck)
Subject: Re: CM> Drums revolving swiftly, and machines that can't add

The core memory was called "Immediate Access Storage" and there were approx. 50
words (equal to 1 drum traack) available in 60 microseconds (as I recall)
cmpared with the drum's word time of 4.8 milliseconds --if the word was under
the read head! And, yes, one could operate directly on words in IAS (or the
console switches, which had the address 8000 and were generally used as the
first instruction, to read a card which contained instructions to read and load
the following cards).
Paul Schneck

            Posted by David S. Bennahum (
                    Moderator: Community Memory
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Sender: "Woody Franke" 
Subject: Jenny?

I'm currently posted to the US Embassy in Canberra, Australia.  This last
weekend I was in Sydney and took time to tour the Powerhouse Museum.  The
museum has a small computer section which is sadly lacking but it does have an
IBM 650 which I believe was shipped to Australia in 1949.

Why a drum instead of a disk?  I think several manufacturers tried the drums.
I remember that Univac developed a magnetic drum to store data in the 1960s.
I also worked on a Scientific Data Systems (SDS) model 1200? that had a
magnetic drum in 1966.  Later on SDS was bought out by Xerox and the name was
changed to XDS (Xerox Data Systems).  One could hear the drum rotate like a
washing machine when it was searching for an address.  It would come to a halt
with a thud and shake the entire drum housing.
Sender: Nelson Winkless 
Subject: CM: Esoteric memory systems

Peter da Silva commented:

> Pretty much anything that can change state quickly enough and retain that
new >state for a while has been used for memory.

Nicely put.

We were briefly involved, thirty years ago, with work on a memory exploiting
a "Moving Barkhausen Discontinuity." As I recall, it's possible to create a
detectable blip in a skinny piece of wire at a point where two magnetic
states meet...and then electrically push that blip along the wire past a
detector. The notion was that a whole lot of blips could be created (and
discreated), storing information that could be pushed at electronic speeds
past the sensor. Compared with the speed of a rotating drum, that could be
might fast and convenient, with no physically moving parts.

Obviously, my technical grasp of this is pretty feeble (and was at the
time), but I loved the name Moving Barkhausen Discontinuity, which has the
same impress-your-neighbors quality as Vonnegut's "Chronosynclastic
Infundibulum," with the added virtue of being real.

I've no idea if anything ever came of the MBD memory work.

Nelson Winkless                   Email:
ABQ Communications Corporation    Voice: 505-897-0822
P.O. Box 1432                     Fax:   505-898-6525
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            Posted by Da