(1) One of the most interesting lines, or circuits, on a bus is the system clock or system timer, which is dedicated to timing the activities of the chips on the motherboard. A quartz crystal on the motherboard, similar to that found in watches, generates the oscillation that produces the continuous pulses of the system clock. Traces carry these pulses over the motherboard to chips and expansion slots to ensure that all activities are synchronized (A+ Guide to Managing & Maintaining Your PC by Jean Andrews, p. 20)