Chipset Functions

A chipset integrates a number of VLSI (very large scale integration) chips that provide much of the PC’s functionality. Each of the chips integrated into the chipset at one time could have easily been a stand-alone chip, but by combining them together into a single chip, the controllers and devices combined into the chipset can share common actions, reduce the physical space required on the motherboard, and reduce cost—all very important considerations in today’s PC market.

Chipset Characteristics

The characteristics of a chipset can be broken down into six categories: host, memory, interfaces, arbitration, south bridge support, and power management. Each of these categories defines and differentiates one chipset from another. The characteristics defined in each of these categories are as follows:

· Host This category defines the host processor to which the chipset is matched along with its bus voltage, usually GTL+ (Gunning Transceiver Logic Plus) or AGTL+ (Advanced Gunning Transceiver Logic Plus), and the number of processors the chipset will support.

· Memory This category defines the characteristics of the DRAM support included in the chipset, including the DRAM refresh technique supported, the amount of memory support (in megabits usually), the type of memory supported, and whether memory interleave, ECC (error-correcting code), or parity is supported.

· Interfaces This category defines the type of PCI interface implemented and whether the chipset is AGP-compliant, supports integrated graphics, PIPE (pipelining), or SBA (side band addressing).

· Arbitration This category defines the method used by the chipset to arbitrate between different bus speeds and interfaces. The two most common arbitration methods are MTT (Multi-Transaction Timer) and DIA (Dynamic Intelligent Arbiter).

· South bridge support All Intel chipsets and most of the chipsets for all other manufacturers are two processor sets. In these sets, the north bridge is the main chip and handles CPU and memory interfaces among other tasks, while the south bridge (or the second chip) handles such things as the USB and IDE interfaces, the RTC (real-time clock), and support for serial and parallel ports.

· Power management All Intel chipsets support both the SMM (System Management Mode) and ACPI (Advanced Configuration and Power Interface) power management standards.

Chipset Built-in Controllers

The controllers and devices included in a chipset are typically those that are common to virtually every PC of the type the chipset is designed to support. The controllers and devices usually included in a chipset are as follows:

· Memory controller This is the logic circuit that controls the reading and writing of data to and from system memory (RAM). Other devices on the PC wishing to access memory must interface with the memory controller. This feature also usually includes error handling to provide for parity checking and ECC (error-correcting code) for every memory word.

· EIDE controller Nearly all mid- to upper-range motherboards now include at least one EIDE connector for hard disks, floppy disks, CD-ROMs, DVDs, or other types of internal storage drives. The EIDE controller typically supports devices with ISA, ATA, and perhaps an ATA-33 or Ultra-DMA (UDMA) interface.

· PCI bridge Like a network bridge that connects two dissimilar networks, this device logically connects the PCI expansion bus on the motherboard to the processor and other non-PCI devices.

· Real-time clock (RTC) This clock holds the date and time on your PC; this is the date and time that is displayed to you on the monitor and is used to date-stamp file activities. This should not be confused with the system clock that provides the timing signal for the processor and other devices.

· DMA (Direct Memory Access) controllers The DMA controller manages the seven DMA channels available for use by ISA/ATA devices on most PCs. DMA channels are used by certain devices, such as floppy disk drives, sound cards, SCSI adapters, and some network adapters, to move data into memory without the assistance of the CPU.

· IrDA controller IrDA (Infrared Data Association) is the international organization that has created the standards for short-range, line-of-sight, point-to-point infrared devices, such as a keyboard, mouse, and network adapters. The IrDA port on your system is that small red window on the front or side of notebook and some desktop computers.

· Keyboard controller A chipset may include the keyboard controller, and many of the newer ones do. The keyboard controller is the interface between the keyboard and the processor. See the previous section for more information on this device.

· PS/2 mouse controller When IBM introduced the PS/2 system, the controller for the mouse was included in the keyboard controller. This design has persisted and usually wherever the keyboard controller is, so is the PS/2 mouse controller. This device provides the interface between the PS/2 mouse and the processor.

· Secondary (Level 2, or L2) cache controller Secondary (L2) cache is located on the motherboard, a daughterboard, or as on the Pentium Pro, in the processor package, and caches the primary memory (RAM), the hard disk, and the CD-ROM drives. The secondary cache controller controls the movement of data to and from the L2 cache and the processor.

· CMOS SRAM The PC’s configuration settings are stored in what is called the CMOS memory. The chipset contains the controller used to access and modify this special SRAM area.