The motherboard chipset appeared in the late 1980s and originally was applied to a group of as many as 6 integrated circuits that combined the functions of up to 80 Small/mid sized ICs in the original PC into a few larger scale chips. The functions included memory management, DMA, interrupt control, the programmable timer, etc. As time went by improvements to circuit fabrication technology allowed the chipset to shrink to two, then to one IC. By the late 1990s, the chip "set" is usually a single IC or a pair of functionally separate chips called Northbridge and Southbridge chipsets.
Further improvements in technology allowed other common functions such as CMOS memory, the Real time clock, the keyboard controller, etc to be included in the chipset IC. By the mid 1990s, motherboards had shrunk from nearly 100 ICs to as few as a dozen -- less if no cache memory was configured.. At that time, common peripheral functions started to be subsumed into the chipset -- serial ports, parallel ports, IDE controllers. Network Interfaces, Sound, USB, and SCSI are incorporated in some chipsets.
Chipsets are usually specific to a specific CPU or set of CPUs. Early chipsets were socketed, but modern ones are almost invariably soldered into the motherboard, and are not replaceable. Chipsets usually contain programmable features that can be controlled through Port 21 if the register configuration of the chipset is known.
Most BIOSes allow some control of chipset features via BIOS Setup functions. Some inexpensive motherboards have BIOSes that allow all the chipset features to be accessed including many that are best never changed.
Return To Index Copyright 1994-2002 by Donald Kenney.