The entire design of the PC is based on the microprocessor chip. The microprocessor can take in data, perform arithmetic operations like addition, subtraction, division or multiplication on the data and send out the result. It also performs comparison operations on data to check if they are equal, or if one is greater than the other. It also has the ability to perform logical operations on data. The microprocessor controls the activities of the various components of the computer and also responds to requests from the peripheral devices; for example, printer signals indicating that it has run out of paper.

Intel Microprocessor 4004

The microprocessor consists of the Arithmetic-logic unit (ALU), the Control Unit and some special purpose storage areas called Registers. The ALU section is where the actual arithmetic and logic instructions are executed. During its ALU operations, the microprocessor holds its intermediate results in special purpose registers. These registers are storage areas which are physically a part of the microprocessor chip. These are not accessible to the programmer.

The control section makes available to the ALU, the requisite data that it needs to work upon. It does this by keeping track of the next instruction to be executed and the address of the data referred to by this instruction. The control also uses some of the special purpose registers of the processor to hold the next instruction and the data addresses.

There are many types of microprocessors available in the market that are manufactured by different companies like Intel, Advanced Micro Devices, Motorola, etc. The most widely-used are the range of Intel microprocessors. The microprocessors in the family of Intel processors are the Intel 8004, 8085, 8086, 8088, 80286, 80386, 80486 and the Pentium. The Pentium is the most powerful microprocessor from Intel.

The capacity of a microprocessor is measured in terms of the number of bits it can send or receive and the number of bits it can process internally. The 8088 is an 8/16 bit processor, indicating that it can send or receive 8 bits of data and internally process 16 bits of data at a time. The 80286 is a 16/16 bit processor. Thus, it is a true 16 bit processor and is faster than the Intel 8088 chip. Also, the 80286 can work in two different modes: the real and the protected. When working in the real mode, the 80286 works just like the 8088. In the protected mode, the 80286 makes available many facilities that are not available on the 8088. For example, it provides features that allow more than one program or task to be executed simultaneously. The protection feature prevents one program from tampering with any part of the memory that does not belong to it.

The 80386 chip has a 32-bit processing capability with a 32-bit data path and, as a result, is much faster than either the 8088 or the 80286 chip. Like the 80286, it can also work in the protected mode.

The 80486 chip was introduced by Intel in late 1989 and for the next four years, enjoyed the distinction of being the best performing microprocessor in the Intel family. The Intel 80486, like the 80386, is a 32-bit processor. It has architectural enhancements, which makes it perform better than the 80386 chip.

The Pentium is a 32-bit processor with a 32-bit data path, and was introduced in 1993. It is three times faster than the 80486, and is considered the best in the Intel family.

Note: DOS is a 16-bit operating system and most applications that run under it are 16-bit applications, including Windows 3.1. Windows NT however, is a 32-bit operating system that runs 32-bit applications. To maintain a degree of compatibility, older 16-bit applications are also allowed to run on the 32-bit platform. But what is required today is not just better hardware that runs applications faster, but also better software that matches the changing hardware.