Wall-clock time, refers to elapsed time as determined by a chronometer such as a wristwatch or wall clock. (The reference to a wall clock is how the term originally got its name.)
wall-clock time differs from time as measured by counting microprocessor clock pulses or cycles. The number of microprocessor clock cycles per second of wall time depends on the microprocessor's clock speed . The microprocessor clock is not a chronometer, but a signal generator that outputs pulses at a high, precise, constant frequency . The microprocessor clock in a 2-GHz computer ticks twice as fast (2,000,000,000 cycles per second) as the microprocessor clock in a 1-GHz computer (1,000,000,000 cycles per second). The so-called computer clock that displays chronological time in terms of the date, hour, minute, and second displays wall time, not the time in microprocessor cycles.
