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By 1987 the information processing power
of electronic computers of the 1960s could be held
in one hand. The Thermal Conduction Module seen
here was the marrow of the large IBM 308X computers.
Six inches square, the TCM had room for up to 133
chips, each with 704 circuits. Each ceramic block
of the material had 28 to 33 differently wired layers.
More than 350,000 holes provided paths for the vertical
wiring for layer-to-layer communication. The chips
were joined to the substrate through a total of
nearly 16,000 contact points, using IBM's unique
chip-joining technology. All that circuitry generated
300 watts of heat -- enough to destroy the chips.
But the heat was drawn off through spring-loaded
aluminum pistons (seen in the cutaway section) that
pressed gently against each chip. In turn, the pistons
were housed in a "hat" filled with helium,
an excellent heat conductor. Chilled water flowing
through a conduit attached to the hat whisked the
heat away. One TCM alone -- there were about two
dozen in a 3081 computer -- packed as much computing
punch as a medium-size System/370 of only a decade
before. (VV2137)
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