Intro to Computer Systems

Chapter 6a: System Expansion

Feature Expansion

In addition to the core processing components of the computer system (the CPU, memory and its support chipset), further functionality and connectivity can be added by expansion cards and other peripheral interfaces.

The most common types of expansion that happen internally (inside the computer's case) are through:

Any type of connection has a maximum bandwidth; this is the maximum amount of data that can travel on it at any one time. We have come across this statistic when discussing memory bandwidth, and the same principles apply to all other connections.

Expansion Cards

Expansion slots offer a way to add extra functionality to a computer system. As the slots are connected directly to the chipset, they offer a fast pathway for information to flow between them and the computer's core internals.

Cards designed to fit into these slots offer many kinds of expansion possibilities. A few examples:

Storage Interfaces

Storage interfaces are connectivity options that are specialised to the task of adding mass storage (e.g. hard disks, DVD drives, etc.) to a system. These interfaces are usually either integrated onto the southbridge of a system chipset, or added to the system through an expansion card.

Most storage-specific interfaces are designed primarily with internal expansion in mind; however some have extensions to the standard to allow for a limited level of external expansion opportunity.

Evolution in Expansion Interfaces

The evolution of storage interface standards has in general been more dynamic than those of expansion cards, as there is a much lower practical barrier to implementing new standards. In the worst case scenario, all that's required is to buy an expansion card that supports the new storage interface.

Compare this to a new expansion card interface, which involves not only new expansion cards, but also the motherboard (electrical side of the expansion interface), and a chipset to support it. In practice, it's virtually impossible to "upgrade" the expansion card interface of a system without building an entirely new computer.