speedometer

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.

[Jargon File]