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PC Structural Design

Imagine an entire PC system sitting in front of you. It has a dozen or so key components, all connected to each other in one way or another. Some are inside the PC and some outside. How do you take this collection of parts and analyze it so that it is easily understandable?

A useful first way is to consider the PC system as a set of different groups of components, each with a particular role to play in overall PC design. Here are the four categories into which I divide the components of the PC at the highest level:

• The "Structure": These are the components that form the physical infrastructure of the PC system. All the other components "fit into" the physical framework that these structural components provide, or connect to it. The structural components must normally be specified together, as they must be physically compatible. The shape and size of these components is called their form factor, and they must be matched. The key structure components are the power supply, case and the physical motherboard (along with its interface components).
• The "Processing Core": These are the solid-state components that do the bulk of the "heavy lifting" inside the PC. They are responsible for the main processing of the PC, and control of the entire system. These components include the chipset and other motherboard controllers, the CPU, system memory, and video card. As with the structure components, these are all intimately related; you can't buy a CPU independently of the chipset, or memory without considering the type of motherboard circuitry, for example.
• The "Independents": These are components that go inside the PC box, but are for the most part independent of the core components responsible for processing. They still must interface with the motherboard and other core devices, but today's machines are sufficiently standardized that these can, within reason, be "mixed and matched" in different systems. Components fitting into this category include hard disk drives and other storage devices, modems, sound cards, communication ports and other internal peripherals.
• The "Externals": These are components and peripherals that connect to the PC box from the outside. Since they are outside the PC case, they are even more capable of being separated from the PC and moved to another similar unit. They can often be purchased entirely separately from the main PC unit itself, and moved to a new PC unit years down the road. Components falling into this category include input devices such as keyboards, mice, joysticks and scanners, and output devices such as monitors, speakers and printers.

While perhaps not a perfect way to divide the parts of a PC up, these four groupings should help you visualize how a PC is structured in the most basic level. They are certainly not completely independent of each other, because of course everything is connected into an overall system. Yet they are different in terms of how they fit into the overall design.

Considering these different groups is also essential for approaching the design and creation of any PC system. The groups show you which components must be specified (and ideally purchased) at the same time. For example, you can't just pick a motherboard and a case and hope they fit together; you have to be sure they are physically compatible. The same goes for the core logic--the CPU isn't something you choose without knowing what memory and chipset you'll be using. But the more independent components, while still requiring attention to ensure compatibility, can in many ways be "added" to the basic design later on. You can use this "hierarchy" to help guide your design decisions.

Next: PC Subsystem Design

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