Hardware Reference
In-Depth Information
Most crystals use a disc-shaped sliver of quartz as a resonator. The disc is contained in a
hermetically sealed evacuated enclosure.
Figure 3.43
shows the interior view of a typical
crystal with a disc-shaped resonator inside. The quartz disc inside has electrodes on each
side, allowing voltage to be applied to the disc. The details are shown in
Figure 3.44
.
Figure 3.43
Figure showing the disc-shaped resonator.
Figure 3.44
Disc-shaped quartz resonator details.
Walter G. Cady was the first to use a quartz crystal to control an electronic oscillator
circuit in 1921. He published his results in 1922, which led to the development of the
first crystal-controlled clock by Warren A. Marrison in 1927. Today, all modern com-
puters have multiple internal oscillators and clocks, some for controlling bus and pro-
cessor speeds and at least one for a standard time-of-day clock.
Modern PC Clocks
A typical PC has at least two crystals on the motherboard; the main crystal controls the
speed of the motherboard and motherboard circuitry, and the other controls the real-time
