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.

