PC's Second Most Important Silicon: The Chipset

Chipset:

If the CPU is the brain of a personal computer, the motherboard is its nervous system -- the foundation or platform that supports and provides the data-transfer connections between the processor, memory, AGP and PCI expansion cards, disk drives, and external peripherals. And next to the CPU, the most important part of a motherboard is its core logic chipset.

One manufacturer, Nvidia Corp., prefers the term "platform processor" to "chipset." It's marketing jargon that makes sense, in that a chipset determines a motherboard's and hence computer's capabilities -- everything from what kinds of peripherals you can plug into it to what kinds of CPU and memory it can use. Nowadays, thanks to TV commercials, even casual home-PC buyers are likely to ask which processor a system has. This article will explain why truly smart shoppers learn which chipset it has, too.

North and South:

A chipset's functions are divided into two groups, which are usually handled by two chips -- the Northbridge and Southbridge, which you can think of as "inner" and "outer" or adjacent to the CPU and peripherals, respectively. Names vary -- Intel calls these components hubs; SiS calls them controllers -- but the purpose is the same: the Northbridge and Southbridge provide data bridges between specific sets of bus peripherals.

Intel's block diagram of its recently introduced 845PE Pentium 4 chipset, reproduced below, illustrates the architecture of most standard chipset designs -- the Northbridge handling the more data-intensive pathways such as the memory and AGP (Advanced Graphics Port or screen display) buses, while the Southbridge takes care of secondary connections such as those to ATA/IDE disk drives and USB peripherals. There is a strict division of duties between the Northbridge and Southbridge, as well as a high-speed interface between the two.

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