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Subject: Dead Media Working Note 03.7
Dead medium: Dead memory systems
From: boneill_AT_allinux1.alliance.net (Bradley O'Neill)
Source: A History of Computing Technology by Michael R.
Williams; Prentice-Hall, 1985.
LOC#QA71.W66 1985
pages 304-305
1. THERMAL MEMORIES
"The idea of thermal memory was tried by A.D.
Booth, who, through the lack of other suitable material
being available in Britain after the Second World War, was
forced to experiment with almost every physical property
of matter in order to construct a working memory. The
device was never put into production because of the
inherent unreliability of the system.
"Booth's thermal memory consisted of a small drum
whose chalk surface was capable of being heated by a
series of small wires. These wires would locally heat a
small portion of the surface of the drum and, as the drum
rotated, these heated spots would pass in front of a
series of heat detectors. When a hot spot was detected, it
was immediately recycled back to the writing mechanism
which would copy it onto a clean (cool) part of the drum.
The back of the drum was cooled (erased) by a small fan so
that, by the time the drum had rotated to a bring the same
area under the heating wires again, a fresh surface was
available to receive the recycled information."
2. MECHANICAL MEMORIES
Built by A.D. Booth in post-WWII, mechanical
memory "(...)consisted of a series of rotating disks,
each of which contained a tiny pin which was allowed to
slide back and forth through the hole, and as the disk
rotated, a solenoid was used to push the pins so that they
protruded from one side of the disk or the other. A small
brush made electrical contact with those pins which were
sticking out of one edge of the disk. It was this brush
which enabled it to read the binary number stored by the
pin positions.
"By putting a number of such disks together on one
shaft, it was possible to produce either a serial storage
unit (where one number is stored on each disk and the
readout is done bit by bit as the disk rotates) or a
parallel storage unit (where one number is stored on the
corresponding positions of a series of disks and the
readout of all the bits of a number takes place at the
same instant)."
(((Booth constructed a 'disk-pin memory device',
which looks like a small typewriter. About 20 reading
heads are lined up along the spool, which houses the
rotating disks. Booth's ARC computer used this technology
at one point in its early development.)))
pages 308-311
3. ACOUSTIC MEMORIES
The first reliable memory system.. Utilized in the
following computers:
EDSAC
EDVAC
UNIVAC 1
the Pilot ACE
SEAC
LEO 1
"The basic concept behind the device was to
attempt to delay a series of pulses, representing a binary
number, for a few milliseconds which, although a very
short time, was a relatively long period as compared to
the electronic cycle time of the machine. After they had
been delayed for a short time, the pulses would be fed
back into the delay system to again store them for a
further short period. Repeated short delays would add up
to a long-term storage."
"The mercury delay-line was developed by William
Shockley of Bell Labs and was improved upon by J. Presper
Eckert, one of the people who designed and built ENIAC....
"(T)he mechanism would take a series of electrical
pulses and convert them into sound waves by the use of a
piezoelectric quartz crystal. The sound waves would then
make their way, relatively slowly, down the mercury-filled
tube. At the far end of the tube, the sound waves would be
detected by another quartz crystal and the pulses,
amplified and reshaped, would then be fed back into the
front of the delay again."
(((Various problems including computer
temperature, modulation/demodulation electronics, and
delay time ultimately doomed this memory format. In the
1950s, advances led to the magnetostrictive delay, extinct
by the 1970s.)))
OTHER DEAD MEMORY STORAGE SYSTEMS:
4. Electrostatic storage (early CRT based systems)
5. Rotating Magnetic Memory (used in proto-disk drives,
as in the 'Mail-a-Voice' recording machine)
6. Static Magnetic Memory (magnetic cores)
Bradley
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