RETROSPECT
Pomerene achieved a 34-hour error-free test of a
two-stage memory on July 28 and 29, 1949, and the
final race to build a working 40-stage memory began.
All 40 memory tubes had to work perfectly at the
same time. Data was processed by operating on
all the digits of a 40-bit word at once, with each bit
assigned the same position in a different Williams
tube, an addressing scheme analogous to handing
out similar room numbers in a 40-floor hotel. This
made the computer 40 times as fast as a serial
processor, but, in the opinion of numerous skeptics,
unlikely to work without one thing or another always
going wrong. “The rig can be viewed as a big tube
test rack,” Bigelow observed.
A 41st monitor stage could be switched over to
mirror any of the 40 memory stages, allowing the
operator to inspect the contents of the memory to
see how a computation was progressing — or why
it had come to a halt. This was later augmented by
a separate 7-inch cathode-ray tube serving as a
7,000-points-per-second graphical display.
Each individual memory tube had its own logbook
recording its health history and any idiosyncrasies
that arose along the way. The memory constantly
had to be “brought back into focus” and the resulting
difficulty in distinguishing memory problems from
coding problems drove many early programmers
near-insane.
“The presence of this leprous element in the
machine [means] that everyone who sits down to
do a problem must be aware of it and be prepared
to be just a little cagey, depending on the problem,”
complained one early user, “for the blips fade in a
fraction of a second and if the problem requires that
you re-use a number before the blip is regenerated,
you get the wrong answer. It is as if a desk calculator
would fail any time the 7th, 8th, and 9th places in a
15-digit number happened to be a three-digit prime
… it just isn’t decent for the operator to have to
worry about how the machine is built.”
Nonetheless, the Williams tube changed the
world. Both the Williams group in Manchester and
the von Neumann group in Princeton agreed to
preclude patent disputes by placing the invention
in the public domain. More than a dozen first-generation copies of the IAS machine were built,
and the second generation included the IBM 701.
Thanks to a small gang of nonconformists, programmers were given a true random-access memory,
where any storage location could be addressed at
180 Make: Volume 10
TOP IMAGE: Logbook page for an individual memory
tube, 1952–1953. The “screenshots” pasted into the
log are direct photographic images captured for
diagnostic purposes. By 1953 there were 53 kilobytes
of random-access memory in the entire world, with
5kB in the original IAS machine.
BOTTOM: Machine log, 11: 45 p.m., 9 September 1954:
“Raster suddenly expanded” and entire memory has
turned to “garbage.” With a diagnosis of “suspect
deflection circuitry,” the engineers (who were running
a numerical evolution experiment for Nils Barricelli)
shut down at 12: 16 a.m.
any time. The digital universe as we know it came
into existence when the address matrix was freed
from the physical restrictions that serial access had
imposed. Only then could code start freely moving
around. All hell broke loose as a result.
Someday, and it may be soon, the flickering light of
the last cathode-ray tube monitor will fade to black,
never to return. For a few seconds, an electrostatic
charge will linger on its surface, a ghostly memory
from a time when cathode-ray tubes ruled the world.
George Dyson, a kayak designer and historian of technology,
is the author of Baidarka, Project Orion, and Darwin Among
the Machines.
