Page 9 - DCAP210_INTRODUCTION__TO_MICROPROCESSORS

Unit 1: Microprocessors and Microcomputers

it consumes the most power. Four-bit devices, while inexpensive, are good only for simple control Notes
applications; in general, the wider the data format, the faster and more expensive the device.
CISC processors, which have 70 to several hundred instructions, are easier to program than RISC
processors, but are slower and more expensive.
Microprocessors have been described in many different ways. They have been compared with
the brain and the heart of humans. Their operation has been likened to a switched board, and to
the nervous system in an animal. They have often been called microcomputers. The original
purpose of the microprocessor was to control memory. That is what they were originally designed
to do, and that is what they do today. Specifically, a microprocessor is “a component that
implements memory.”

A microprocessor can do any information-processing task that can be expressed, precisely, as a
plan. It is totally uncommitted as to what its plan will be. It is a truly general-purpose information
processing for microprocessor.

Computer’s performance is also influenced by the system bus architecture,
memory used, type of the processor and software program being running.
Pentium 4 is the fastest type of the Intel’s processor that contains 125,000,000
transistors and operates at the speed of 3.6 GHz.

1.2 Microcomputer

The term microcomputer is generally synonymous with personal computer, or a computer that
depends on a microprocessor. Microcomputers are designed to be used by individuals, whether
in the form of PCs, workstations or notebook computers. A microcomputer contains a CPU on a
microchip (the microprocessor), a memory system (typically ROM and RAM), a bus system and
I/O ports, typically housed in a motherboard.

Intel’s first microcomputer appeared in November 1971:
Intel delivered two different microcomputers five months apart: the MCS-4, emphasizing low
cost in November 1971, and the MCS-8, for versatility in April 1972. “The MCS-4 and MCS-8
CPU chip sell in quantity for less than ` 1000 each, and are powerful alternatives to random
logic”. These two Microcomputer Systems (MCS) were aimed at two very different markets. One
would eventually lead to the under ` 4500 controller, the other would be the engine for a versatile
personal computer (PC). By analogy it was like creating the “motorbike” and the “station wagon”
at the same time. The advertised prophecy of “a new era” became fulfilled over the subsequent
20-year period.

1.2.1 Automobile Analogy
Our challenge was how to scale down a general purpose computer to fit on to a chip. Imagine
that the only passenger vehicle in existence is an eight-passenger van costing ` 2250 000. At first
it would be difficult to imagine ` 1000 version of this vehicle. The specifications would need to be
drastically reduced to meet the price goal. Some ideas to consider:
1. reducing capacity by 75%
2. reducing speed by 90%
3. reducing range by 75%
The golf cart might be the result. However, if golf carts are unknown at the time, it is not easy to
envision how to scale down a van.

1.2.2 Intel MCS-4 4-B Chip Set
Although Intel began as a memory chip company, in 1969 we took on a project for Busicom of
Japan to design eight custom LSI chips for a desktop calculator. Each custom chip had a specialized

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