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Among the novel features of the Whirlwind was the use of 16 math units op-
erating in parallel, which made the Whirlwind sixteen times faster than computers
using serial math.
The Whirlwind initially used mercury delay lines for memory. In a mercury
delay line, a tube of liquid mercury had a microphone at one end and a transducer
at the other end. Pulses were sent into the mercury and moved through it at the
speed of sound until they were received at the other end. The signals were then
amplified and sent back again, so the memory recirculated. The speed of sound
varied with temperature, so the mercury delay lines did not operate at constant
speeds, which caused problems. In addition to erratic performance, mercury is
poisonous, so broken tubes were an occupational hazard of some significance.
Both mercury delay lines and cathode ray tubes were too slow and unreliable
to be effective as computer memory devices. The project manager for Whirlwind
was Jay Forrester. He had read about a new form of magnetic material and ordered
samples. He experimented in his spare time at a workbench in the corner of the lab.
After several months Forrester developed magnetic core memory. His first proto-
type consisted of thirty-two cores, each about 3/8 of an inch in diameter.
Forrester turned over the memory core project to a graduate student, and within
two years, magnetic core memory was ready to go commercial to replace mercury
delay lines and cathode ray tubes as the memory storage of choice for digital com-
puters. Later, IBM developed the magnetic core concept as well as machines to
speed up core memory construction.
The Whirlwind computer would be the basis of the SAGE air-defense system in
the next decade and some of its technology would also find its way into SABRE,
although improved by IBM. (SABRE stands for Semi-Automated Business Re-
search Environment, which is a somewhat convoluted name perhaps selected
merely to use the acronym “sabre.”)
An informal use of the Whirlwind computer was the development of a “boun-
cing ball” game in about 1949 by a researcher named Charley Adams. This was a
precursor to later games such as Pong that would generate billions in revenue. It
is interesting that computer games started to appear almost as soon as computers
themselves.
Eckert and Mauchly formed the Eckert-Mauchly Computer Company (EMCC)
in 1949 and it later became Univac. This was the world's first pure digital com-
puter company.
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