1.9. System Clock

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A system clock coordinates the activity of the server components. The clock is actually a crystal. When electrical current is applied to the crystal, it vibrates at a constant rate. The number of vibrations is measured in megahertz (MHz).

Each vibration is known as a clock cycle or clock tick. The clock cycles act as a sort of drumbeat that drives the work of all other components. Every action a component makes takes place on a clock tick.

Some components work faster than others, getting their work done in fewer clock cycles. The challenge in server design is to connect all the components in a way that provides a constant data flow through the system but minimizes bottlenecks. The design of the server, combined with the user configuration of the server, determines whether a subsystem works to enhance performance or works as a bottleneck to restrict overall performance.

Data flow in a server can be viewed in a hierarchical, fastest-to-slowest, logical block diagram. Data must move through the system effectively from fast to slow and back. To keep the faster subsystems (processors and memory) working efficiently, the system depends on controllers, memory buffers, parallel buses, and concurrent read and write processes.

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    HP ProLiant Servers AIS. Official Study Guide and Desk Reference
    HP ProLiant Servers AIS: Official Study Guide and Desk Reference
    ISBN: 0131467174
    EAN: 2147483647
    Year: 2004
    Pages: 278

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