= S =
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
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.
--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.