[ The PC Guide | Introduction to
the PC | PC Fundamentals ]
Signaling, Clocks and Synchronous Data Transfer
Your PC performs millions of operations every second. Not only is the main system
processor executing instructions, data is being transferred from the system memory,
storage devices are being read and written, input and output devices are sending and
receiving information... There's quite a bit going on inside that box, a veritable factory
of busy little workers, moving data around. :^)
Obviously, all of this activity must be coordinated and managed. The PC's internal
circuits use a special system of communications to control all of these activities and
ensure that the various parts of the computer are "on the same page of the
play-book", so to speak. These communications are performed using special control
signals, as well as clock signals that synchronize components and set the pace for most
internal operations.
In order to grasp the operation of many of the technologies within the PC, it's
important to understand at least the basics of how these signals and clocks work. The use
of signals and clocks is common to many different areas of the PC's operation, from the
CPU to the system memory, to video and storage interfaces.
In this section I provide an introduction and high-level explanation of how signaling
and clocks work within the PC. I begin by discussing basic concepts related to voltage
levels and signaling within PC circuits. I then explain clock signals and how they work,
and also describe how multiple clocks are used within the PC. Then, I describe the way
that the clock is used to control data transfer across buses and interfaces.
 Next: Voltage Levels and Signaling
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