A+ Certification: Part 2 – Hardware: System Architecture

Section Objectives

After you complete this section you will:

Understand what a system board is and identify different parts on it.

Understand what the function of a CPU is.

Understand the differences between CPUs.

Be able to identify different sockets and their corresponding CPUs.

Understand what LIF, ZIF, SEPP, and SECC are in regards to upgrading CPUs.

General System Architecture Overview

System Architecture is a broad topic in regards to computers.

There are many components which make up a computer. Each one is necessary to the operation of the computer, which makes each one important in terms of troubleshooting issues and difficulties.

At the heart of the computer is the motherboard and its heart the central processing unit (CPU). The CPU is responsible for most of the processing of software applications, directing of data traffic inside the computer, and other operations of the computer. An example of a CPU is a Pentium III.

The computer also needs to allow its user to change its base settings and store those settings. Its BIOS (Basic Input Output System) contains the base level instructions for the computer and has a setup program to change any user-defined settings such as hard drive type, power management settings, or IRQ settings. The BIOS stores its data in the CMOS (Complementary Metal Oxide Semiconductor).

The motherboard/system board also contains RAM (Random Access Memory). RAM is used to load your operating system and software applications to be able to utilize them while you are using your computer system. RAM has extremely fast transfer rates.

The system board also has expansion buses allowing you add expansion cards to increase communication capabilities, expand viewing features, or use the computer more effectively. Example expansion boards include an Ethernet card, a 64 Mb video card, or a IEEE1394 Firewire expansion card.

In addition, PCs have storage devices which allow you to store and retrieve data. A storage device may be a hard drive, a floppy drive, or an optical drive.

The System Board

In the System Board course, you learned (or will learn) what the system board is and a general description of the components on the system board. Here is a picture of a motherboard and its components, you should be aware of the general “look” of the different components and be able to identify them for exam questions:

The CompTIA A+ Hardware exam will present you a question or series of questions of identification of parts on an image of a motherboard. You should be aware of what different components look like.


The CPU is the central processing chip of the computer and processes instructions from the operating system and the software running on the computer. As the heart of the computer, most of the instructions and data flows through it.

There are many different manufacturers of CPUs including Intel, AMD, IBM (PowerPC), Sun, HP, and more. Within those manufacturers, you have several different models of CPUs such as the Intel Pentium or the AMD Athlon. As 95% of the computer world relies on Intel compatible processors, most of the A+ Hardware Service technician exam covers those chips, so we will focus on those.

Characteristics of a CPU

Chip Speed

The processor contains millions of transistors. The CPU is measured by its clock speed in MHz. One Megahertz is one million cycles per second. The first IBM PC CPU, the Intel 8088, ran at 4.77 MHz. Today’s PCs exceed 2 GHz (2,000 MHz!)

Math Coprocessor

Contained within the chip is a math coprocessor which handles floating point calculations, like algebra and statistics. The math coprocessor is also referred to as the FPU (Floating Point Unit). Earlier Intel chips had an additional chip which handled the math functions, but the Pentium line has had the functions built-in.

Cache Memory

Most processors have an internal cache which stores frequently used data and instructions. Cache is broken up into two classificatio

ns, L1 which is internal cache and L2 which is the external cache.


Each processor has buses which work with it.

The external bus, also called the system bus, allows the processor to connect with other devices such as expansion cards and devices.

Buses consist of two parts: data bus and address bus. The data bus transfers the information and the address bus tells where the information should go.


Here is table of the different chip types and their characteristics (we included PowerPC for comparison purposes):

CPU Speed (MHz) Data Bus (Bits) Address Bus (Bits) L2 Cache Addressable Memory Transistors
8088 4.77 8 20 0 1 MB 29,000
80286 8-12 16 24 0 16 MB 134,000
80386SX 16-20 16 32 0 4 GB 275,000
80386DX 16-33 32 32 0 4 GB 275,000
80486SX 16-33 32 32 8 Kb 4 GB 1,185,000
80486DX 25-50 32 32 8 Kb 4 GB 1,200,000
486DX2 33-66 32 32 8 Kb 4 GB 1,200,000
486DX4 75-100 32 32 8 Kb 4 GB 1,600,000
Pentium I 60-166 64 32 16 Kb 4 GB 3,100,000
Pentium MMX 166-233 64 32 32 Kb 4 GB 4,450,000
Pentium Pro 120-200 64 36 288 Kb 64 GB 5,500,000
Pentium II 233-450 64 36 512Kb 64 GB 7,500,000
Celeron 500 + 64 32 128Kb 4 GB 7,500,000
Pentium III 450-1,000 64 36 256Kb 64 GB 9,500,000
Pentium III Xeon 500-1,000 64 32 256Kb-2Mb 64 GB 28,100,000
Pentium IV 1,400 + 64 64 256Kb 64 GB 55,000,000
Itanium 1,000 + 64 64 L3 – 4Mb 64 GB 25,000,000
Athlon 850-1,200 64 32 256Kb 4 GB 22,000,000
Athlon XP 1,600 + 64 64 384Kb 64 GB 37,500,000
Power PC G3 233-333 64 64 512Kb, 1Mb 64 GB 6,500,000
Power PC G4 400 + 64 64 1Mb 64 GB 10,500,000

The A+ Hardware exam will delve into some of the details in this chart. Things to take notice of is the Data Bus, Address Bus, and Addressable Memory. You will probably be tested on these items.


CPUs are designed in different sizes and therefore are mounted in different “sockets” on the motherboard. 486 and newer chips have a heat sink and fan mounted to them to dissipate the heat generated by the chip.


Socket Pins Processors Upgrade
0 168 486DX 486DX2 / 486DX4
1 169 486DX, 486SX 486DX2 / 486DX4
2 238 486DX, 486SX, 486DX2 486DX2/4, Pentium
3 237 486DX, 486SX, 486DX2, 486DX4 486DX2 / 486DX4
4 273 60/66 MHz Pentium Pentium
5 320 Other Pentium Pentium
6 235 486DX4 Pentium
7 321 Other Pentium Pentium
8 387 Pentium Pro Pentium Pro
Slot 1 242 Pentium II, Celeron Pentium II, Celeron
Slot 2 330 Pentium II, Xeon Pentium II, Xeon
Slot A 462 Athlon, Duron (AMD) Athlong, Duron (AMD)
Socket 370 370 Celeron Celeron
Socket 423 423 Pentium 4 Pentium 4

Upgrading Your CPU

There are several types of upgrade methods for CPUs: ZIF (Zero Insertion Force), LIF (Low Insertion Force) sockets, SECC (Single Edge Contact Cartridge), and SEPP (Single Edge Processor Package). ZIF Sockets have a mounting bar attached.

ZIF is a common upgrade type with Pentiums (the most common type of all motherboards). LIF is more common among older 486 style systems. SECC is common among Pentium II and Xeon (Slot 2), while SEPP is common with Pentium II, Pentium III, and Celerons (Slot 1).

Zero Insertion Force

Single Edge Processor Package

Single Edge Contact Catridge

After you have studied this section you should:

Understand what a system board is and identify different parts on it.

You should be able to identify the parts of a motherboard as explained in this diagram.

Understand what the function of a CPU is.

A CPU, or Central Processing Unit, is the “heart” of the computer. Most data processing, software instructions, and operating system commands run though it.

Understand the differences between CPUs.

Be able to identify the differences between different CPUs.

Be able to identify different sockets and their corresponding CPUs.

Understand what LIF, ZIF, SEPP, and SECC are in regards to upgrading CPUs.

ZIF (Zero Insertion Force), LIF (Low Insertion Force), SEPP (Single Edge Processor Package), and SECC (Single Edge Contact Cartridge) are four types of upgrade methods on motherboards for CPUs (or more specifically four categories of slots CPUs fit into).

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