The A+ Exams Guide: (Exam 220-301), (Exam 220-302) (TestTakers Guides)

CPUs are generally faster than the devices they communicate with. So that smooth communication can take place between CPUs and peripheral devices, interfaces known as chipsets have been developed to handle this transition or buffering of information. Early computers used separate chips to control the transition of data for specific tasks. Some of the early chips and notable controller interfaces were:

• The bus controller chip. Handles or ‘supervises' the flow of information on the different motherboard buses.

• The Direct Memory Address (DMA) controller. The DMA controller allows devices to utilize addressed memory without interacting with the CPU.

• Math coprocessor. Supervises the flow of information between the math coprocessor and the CPU.

Super I/O Controller

The super I/O controller was a great advancement. It combined the functions of older, separate controller chips into one ‘smart chip.' The super I/O controller chip became a welcomed standard. Some of the major functions controlled by the super I/O include control of serial port Universal Asynchronous Receiver/Transceiver (UART), control and support for floppy disk and tape drives, and control functions related to parallel ports and their enhanced capabilities.

Chipset Controllers (Built-In)

Chipsets are designed to support specific devices, motherboards, CPUs, and computers that they will control. Several built-in devices and controllers included with common chipsets are worth mentioning.

• Enhanced Integrated Drive Electronics (EIDE) controller. The EIDE (or IDE) controller is used to communicate and support devices such as hard disk drives, floppy disk drives, CD-ROMs, and other storage devices. Most computers today have chipset support for two EIDE onboard controllers.

• Memory controller. The memory controller controls the flow of data in and out of memory. Devices that need access to the system memory or RAM must first pass through this controller.

• PCI bridge. As mentioned in Chapter 2, PCI bridging, or north and south bridge, is used to connect the PCI interface on the motherboard with older devices, such as ISA.

• DMA controller. This manages the availability and support for ISA and AT Attachment (ATA) devices. (ATA is a set of rules or specifications that apply to the IDE controller. Both are described in Chapter 7.)

• SCSI adapters, network interface cards, and sound cards. All of these use DMA channels to move data in and out of system memory without assistance from a CPU. This controller provides the ability for the previously mentioned devices to access the system memory. SCSI adapters are discussed in Chapter 8.

• Real-Time Clock (RTC). Controller support is provided for the RTC. The RTC controls system date and time.

• PS/2 mouse. This controller provides a direct interface between the PS/2 mouse and the processor.

• Keyboard controller. Controls functions between the keyboard and the CPU.

• IRDA (Infrared Data Association) controller. Infrared controller packaged with most laptop computers.

RISC vs. CISC

There are two important terms that apply to the programming and instruction sets of chipsets: Reduced Instruction Set Computer (RISC) and Complex Instruction Set Computing (CISC).

RISC is a technology used in high-end computing systems. It uses a limited number of instructions and fewer transistors than CISC does. The result is a less expensive chipset. Most Sun computing systems incorporate RISC technology.

Most conventional computing systems utilize CISC. CISC architecture is capable of supporting many more instructions than RISC. Pentium systems utilize CISC technology.