The the late 1960s and early 70s, there was much talk about "generations"
of computer technology. This photo illustrates what were commonly known
as the three generations:
- First generation: Vacuum tubes (left). Mid 1940s. IBM pioneered the
arrangment of vacuum tubes in pluggable modules such as the one shown here on
the left. The IBM 650 was a first-generation computer.
- Second generation: Transistors (right). 1956. The era of miniaturization
begins. Transistors are much smaller than vacuum tubes, draw less power, and
generate less heat. Discrete transistors are soldered to circuit boards like
the one shown, with intereconnections accomplished by stencil-screened
conductive patterns on the reverse side. The IBM 7090
was a second-generation computer.
- Third generation: Integrated circuits (foreground), silicon chips contain
multiple transistors. 1964. A pioneering example is the ACPX module used in
the IBM 360/91, which, by stacking layers of silicon
over a ceramic substrate, accommodated over 20 transistors per chip; the chips
could be packed together onto a circuit board to achieve unheard-of logic
densities. The IBM 360/91 was a hybrid second- and third-generation
Omitted from this taxonomy is the "zeroth" generation computer based on
metal gears (such as the IBM 407) or mechanical relays
(such as the Mark I), and the post-3rd generation
computers based on Very Large Scale Integrated (VLSI) circuits.
Photo: IBM .
Frank da Cruz / email@example.com /
Columbia University Computing History /