speedometer
speedometer: n. A pattern of lights displayed on a linear set
of LEDs (today) or nixie tubes (yesterday, on ancient mainframes).
The pattern is shifted left every N times the operating system goes
through its main loop. A swiftly moving pattern indicates that
the system is mostly idle; the speedometer slows down as the system
becomes overloaded. The speedometer on Sun Microsystems hardware
bounces back and forth like the eyes on one of the Cylons from the
wretched "Battlestar Galactica" TV series.
Historical note: One computer, the GE 600 (later Honeywell 6000)
actually had an _analog_ speedometer on the front panel, calibrated
in instructions executed per second.
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