Some useful information The basics of buying a personal computer system

(Tltis article was thoroughly studied by Tom's father)

Introduction

There are many different kinds of computers to choose from and finding the one that is right for you and fits your budget can be difficult. The purpose of this text is to describe the parts of the computer and the benefits and pitfalls of these parts so that you can make an educated decision on your computer purchase.

PC versus Macintosh

The two major types of computer systems are PC's and Ma­cintosh. There are advantages and disadvantages of both. The Ma­cintosh is generally more user friendly than the PC and many schools are using the Macintosh. Macintosh is also popular in the advertising and graphic arts market. Many advertising agencies and graphic artists use the Macintosh because of the easy operat­ing system and graphics software available for Macintosh.

The PC is more widely used in the home and business, and there is much more software available for the PC compared to the Macintosh.

Taking Computer for Granted

Where to buy your PC

Computers are available from the variety of sources. In the USA the first place you would think to look are the big retailers, such as Best Buy, Circuit City, CompUSA, or others. The big retailers offer a variety of different computer choices and can be easy to shop at. You pick the computer you want, pay for it and walk out the door. Another reason to shop at a big retailer is convenience, especially if you have a problem and you need to return or exchange your com­puter. You can find good deals and sales at the big retailers.

Another way to buy a computer is through a mail or order company or directly from the manufacturer. With a mail order com­pany you may have to wait a little longer to get your computer, but this is not always bad. When you order a computer you can get the exact computer that you are looking for. You can make up your or­der so that you get all the things you need in the computer. One down side to ordering a computer through the mail is if you have a problem, you may have to send it back, and wait for a replacement.

Two things to check for with any purchase, that many people overlook are:

1. Does the manufacturer have a toll free technical support phone number?

2. Does the company charge a fee for using the technical sup­port?

Components of a computer

A computer is a complex machine that contains of many dif­ferent components. When buying a computer, you should know what these parts are and what they do. This will help you to know what to look for in a quality computer (Fig. 1).

CPU

The CPU, or central processing unit, is the brain of the com­puter. The CPU controls all the action that occurs inside the com­puter. In detail, the processor consists of the following items:

• The control unit (CU) which coordinates the processing steps. 102

UNIT 4

• The arithmetic / logic unit (ALU) which performs calcula­tions and make decisions. The registers which represents a small but very fast auxiliary memory within the processor.

• The cache which is a fast buffer memory between the proces­sor and the actual main memory.

Fig. 1 Basic Computer Architecture

DISC

ARITHMETIC/ LOGICAL UNIT

DISC

CONTROLOLLER

MAIN MEMORY

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CONTROL

UNIT

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REGISTERS

VIDEO CONTROLLER

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DISPLAY

RAM

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KEYBOARD CONTROLLER

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KEYBOARD

Taking Computer for Granted

The operation of processor is driven by high-frequency system clock. In a 933 MHz (MHz = million Hertz) Pentium III processor, the clock beats 933 million times per second and the processor can perform mostly 933 million instruction per second. Different instructions take a different amount of clock cycles. Some instructions may be performed in one cycle, others in many more cycles.

Moor's law

For thirty years, the speed of processor clocks have approx­imately doubled every 18 month and we can expect this trend to continue for the next decade until physical limits are reached.

Processors have registers. Each of them may hold a com­puter word. The registers operate at the speed of the processor. It means that in each clock cycle a register may be read or writ­ten. However the processor operates much faster than the main memory. In order to prevent the processor being slowed down by reading or writing from the main memory, the cache is in­serted between main memory and processor. Whenever the processor issues a request for a memory location, the cache loads a sequence of words containing this location from the main memory and holds it locally for further use. The cache op­erates at processor speed. When the cache becomes full, it writes words (line), which have not been used for a long time back into main memory.

Cache and main memory are coupled by the system bus, a communication unit which combines multiple system devices.

The program executed by the processor is stored in the main memory. It consists of a sequence of machine instructions each of which is encoded in a computer word.

The program counter is a special processor register, which holds the address of the next instruction to be executed.

The operation of the processor is a continuous cycle of the following steps coordinated by the control unit:

• fetch the instruction referenced by the program counter from the main memory;

UNIT 4

• decode the instruction and increment the program counter to reference the next instruction in sequence;

• execute the instruction.

This operation principle is called the von Neumann architec­ture after John von Neumann who invented the concept in 1945.

CPUs come in different types and speeds. Intel, Cyrix, and AMD are the three main manufacturers of CPUs. Intel is the market leader, and will probably stay that way for quite some time. The Cyrix and AMD offerings are usually comparable to the latest Intel CPUs, however, performance is usually slightly below that of Intel. It is recommended buying one step behind the latest technology. It is here that you find the best value for your money. The newest technology is always the most expen­sive, and when a new chip comes out, the previous model al­ways drops in price. It's advisable not to buy anything more than two steps behind the latest technology. Technology changes quickly, and you don't want to buy a computer that will become outdated too quickly.

CPU types

It is absolutely beyond one's reach to give specific informa­tion regarding CPUs because this information has a tendency to get outdated within a few months. It means that if we give you an appropriate advice now, when making this book, it might have been «old fashioned» by the time the book will be issued. Hence, the general advice given above is more timeless.

Processor speed is indicated after the brand of the chip. For ex­ample a Pentium II 400 runs at 400 MHz. MHz stands for Mega­hertz, which put simply, is how fast the computer runs. The higher the MHz, the faster the computer. There are many speeds availa­ble: Pentium III, Pentium IV and so on.

New, faster processors are always in development, and as faster processors become available many of the slower processors are phased out.

Taking Computer/or Granted

Date: 2015-12-11; view: 987