Stacking Up the Chipsets

Stacking Up the Chipsets

The bus structures and interfaces supported by the motherboard and CPU are controlled by functions included on the chipset. The chipset is a group of chips that together help the processor and other peripheral devices plugged into the motherboard communicate with each other. The chipset controls the bits (data, instructions, and control signals) that flow between the CPU and system memory over the motherboard’s buses. The chipset also manages data transfers between the CPU, memory, and peripheral devices. It also supports the expansion bus and any power management features of the system. However, the chipset contains only enough instructions to issue control commands to device drivers, which actually control the peripheral device.

Chipsets are integrated into the motherboard and usually cannot be upgraded without changing the entire motherboard. A PC’s chipset is matched to the motherboard and the CPU as a set. Usually, a given chipset is matched to a single processor type; however, some chipsets support more than one processor. Along this line, you often see the chipset referred to by the CPU’s mounting on the motherboard, for example, Socket 7 chipsets, Socket 370 chipsets, or Slot A chipsets.

At one time, a chipset consisted of several smaller single-purpose controller chips. Each separate controller, which could be one or more chips, managed a single function, such as controlling the cache memory, handling interrupts, or managing the data bus. Today’s chipset combines this set of controller functions into one or two larger, multifunction chips. VLSI (very large-scale integration) has allowed these many chips to be combined into one or two chips.

Chipsets, especially two-chip chipsets, are divided into a North Bridge (the larger chip) and a South Bridge (the smaller chip). The North Bridge provides support and control for main memory, cache memory, and the PCI bus controllers. The South Bridge provides control for peripheral devices and those controllers that are not essential to the PC’s basic functions, such as the serial port controller.

The chipsets are not the only controller sets on the motherboard. The most prominent controller sets are the keyboard controller and a superset of input/output device controllers called the Super I/O controller. The Super I/O chip combines controllers that are common to all systems. Controller chips are also found on many high-end devices and adapter cards.

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