Microprocessor

A microprocessor is a processor whose elements are miniaturized into one or a few integrated circuits contained in a single silicon microchip. It executes instructions. In a microcomputer, the central processing unit (CPU) is held on a single microprocessor. In order to function as a processor, it requires a system clock, primary storage, and power supply.
Several important lines of microcomputers use some families of microprocessor chips. Intel and Motorola are the major companies that produce important microprocessors for IBM compatible and Macintosh computers.

Microprocessor Capacity

The capacity of a microprocessor chip is represented in word sizes. A word size is the number of bits (e.g., 8, 16, or 32 bits) that a computer (CPU) can process at a time.
If word has more bits, the computer (CPU) are more powerful and faster. For example, a 16-bit-word computer can access 2 bytes (1 byte = 8 bits) at a time, while a 32-bit-word computer can access 4 bytes at a time. Therefore, the 32-bit computer is faster than the 16-bit computer.

CISC and RISC Chips

• CISC Chips: CISC stands for Complex Instruction Set Computer. It is pronounced "sisk." CISC is a computer architecture that has large sets of instructions. CISC machines have several hundred instructions. Intel's Pentium-chip uses CISC design.

• RISC Chip: RISC stands for Reduced Instruction Set Computer. RISC is a computer that executes a few number of instructions. In RISC, most programs generally use only a few instructions. This architecture has a small number of instructions built into the circuits and if those basic instructions are made to execute faster, then RISC computers increase performance. Although RISC machines are only around 30% faster than their CISC machines, RISC chips are less expensive to produce. That is, RISC is less expensive per MIPS.

• Controversy: The proponents of RISC claim that its lower cost and speed are an extreme advantage, while the opponents claim its improvements are not great. The opponents believe that new machine languages and greater performance improvements are going to come. Besides, the reduced instructions make software (e.g., compilers) generate more code to do. Thus, the choice is not obvious.

Central Processing Unit (CPU)

The central processing unit (CPU) is the computing part of the computer that interprets and executes program instructions. It is also known as the processor. In a microcomputer, the CPU is contained on a single microprocessor chip within the system unit. The CPU has two parts: the control unit and the arithmetic-logic unit.

Additional storage units called registers within control unit and ALU help make processing more efficient.

• Control Unit: A control unit is the circuitry that locates, retrieves, interprets and executes each instruction in the central processing unit. The control unit directs electronic signals between primary storage and the ALU, and between the CPU and input/output devices.

• Atithmetic-Logic Unit (ALU): ALU is a high-speed circuit part in the CPU. The arithmetic-logic unit (ALU) performs arithmetic (math) operations, logic (comparison) operations and related operations. The ALU retrieves alphanumeric data from memory and then does actual calculating and comparing. It sends the results of the operation back to memory again.

Chips: Achip is an integrated circuit. Microscopic circuit board is engraved in a chip made by silicon. Chips are approximately 1/16- to 1/2-inch square and about 1/30-inch thick. Chips hold a few dozen to several million transistors. For example, an Intel Pentium chip has 3.2 million and Pentium Pro has about 6 million transistors. A chip is also called an integrated circuit, microelectronic, semiconductor, or silicon chip.

Peripheral: A peripheral is any hardware device connected to, controlled by and communicates with a particular computer. It is also called peripheral device and peripheral equipment. For example, it is an input/output unit such as a keyboard, monitor, printer, scanner and mouse. Another example is an auxiliary storage device such as a disk drive, tape drive and optical disk drive.

MIPS: MIPS stands for Million Instructions Per Second. This is the execution speed of a computer. For example, 0.3 MIPS is 300,000 instructions per second. A large mainframe works at 10 to 50 MIPS, whereas a typical microprocessor can perform at around 0.05 MIPS. However, it must be taken carefully. MIPS rate, which is tied to the computer's clock speed, is only one factor in overall performance. Bus and channel speed, disk and memory speed, memory management techniques and operating system also determine total performance of a computer system.

Coprocessor chip: This is one of the specialized processors. A mathematics coprocessor chip that assists the main processor can help a CPU do very fast mathematical computations. The coprocessor is controlled by the main microprocessor.

Registers: A register is a small, high speed circuit that builds special high speed staging areas. This circuit holds data and instructions of internal operation temporarily during processing. They are parts of the control unit and ALU rather than primary storage. Register can handle addresses and values much faster than primary storage can.