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.
CPU
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.
Buses
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.
CPUs
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
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.
Sockets
| 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).
