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This chapter is from the book

This chapter is from the book

How Computers Work, 10th EditionHow Computers Work, 10th Edition

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This chapter is from the book

This chapter is from the book

How Computers Work, 10th EditionHow Computers Work, 10th Edition

Learn More Buy

How PCI-Express Breaks the Bus Barrier

APPLICATIONS, such as streaming video and photo editing, put heavy demands on PCs to move vast amounts of data ever quicker. Until recently, our PCs were bogged down as data was trundled among components by outdated buses—the peripheral components interconnect (PCI) and the accelerated graphics port (AGP). Even the fastest of them, AGP, which spewed out 2.134 gigabytes a second, couldn’t keep up with the demands of real-time—photorealistic animation that needs values for the colors of millions of pixels pushed through the circuits 60 times or more each second.

The solution is a bus architecture that uses both parallel and serial transfers. It’s called PCI-Express, or PCI-E.

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Goodbye to the Party Line

In the older PCI bus, all the devices share the same parallel circuits and receive the same data. The data includes an identifier that says which device the signals are destined for. All other devices simply ignore them. But like telephone users on a party line, the components can’t receive data while some other device monopolizes the connection. The links in PCI-E are point-to-point. The chipset uses a crossbar switch to route incoming signals from one point to another down circuit lines dedicated to specific components. Data goes to several components at the same time. It’s like talking on a private, single-line phone.

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