The case of a desktop computer houses the internal components such as the power supply, motherboard, central processing unit (CPU), memory, disk drives, and assorted adapter cards.

Cases are typically made of plastic, steel, or aluminum and provide the framework to support, protect, and cool the internal components. A device form factor refers to its physical design and look. Desktop computers are available in a variety of form factors including:

Horizontal case

Full-Size Tower

Compact Tower

All-in-one

This list is not exhaustive, as many case manufacturers have their own naming conventions. These may include super tower, full tower, mid tower, mini tower, cube case, and more.

Computer components tend to generate a lot of heat; therefore, computer cases contain fans that move air through the case. As the air passes warm components, it absorbs heat and then exits the case. This process keeps the computer components from overheating. Cases are also designed to protect against static electricity damage. The computer’s internal components are grounded via attachment to the case.

Note: Computer cases are also referred to as the computer chassis, cabinet, tower, housing, or simply box.

Select the arrows below for more information about different types of computer cases.

Horizontal case

This computer case is horizontally oriented on the user's desk with the monitor often positioned on top and was popular with early computer systems. This form factor is often used for home theater PCs (HTPCs).

Complete 1.2.1.2 Power Supplies1.2.1.2 Power Supplies

Electricity from wall outlets is provided in alternating current (AC). However, all components inside a computer require direct current (DC) power. To obtain DC power, computers use a power supply, as shown here, to convert AC power into a lower voltage DC power.

The following describes the various computer desktop power supply form factors that have evolved over time:

Advanced Technology (AT) – This is the original power supply for legacy computer systems now considered obsolete.

AT Extended (ATX) – This is the updated version of the AT but still considered to be obsolete.

ATX12V – This is the most common power supply on the market today. It includes a second motherboard connector to provide dedicated power to the CPU. There are several versions of ATX12V available.

EPS12V – This was originally designed for network servers but is now commonly used in high-end desktop models.

Incomplete 1.2.1.3 Connectors1.2.1.3 Connectors

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Select the arrows below for more information about different connectors.

Connectors

A power supply includes several different connectors, as shown here. These connectors are used to power various internal components such as the motherboard and disk drives. The connectors are “keyed” which means that they are designed to be inserted in only one orientation.

Complete 1.2.1.4 Power Supply Voltage1.2.1.4 Power Supply Voltage

The different connectors also provide different voltages. The most common voltages supplied are 3.3 volts, 5 volts, and 12 volts. The 3.3 volt and 5 volt supplies are typically used by digital circuits, while the 12 volt supply is used to run motors in disk drives and fans.

Power supplies can also be single rail, dual rail, or multi rail. A rail is the printed circuit board (PCB) inside the power supply to which the external cables are connected. A single rail has all of the connectors connected to the same PCB while a multi rail PCB has separate PCBs for each connector.

A computer can tolerate slight fluctuations in power, but a significant deviation can cause the power supply to fail.

Incomplete 1.2.1.5 Check Your Understanding - Cases and Power Supplies1.2.1.5 Check Your Understanding - Cases and Power Supplies

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Incomplete 1.2.2 Motherboards1.2.2 Motherboards

Complete 1.2.2.1 Motherboards1.2.2.1 Motherboards

The motherboard, also known as the system board or the main board, is the backbone of the computer. As shown in the figure, a motherboard is a printed circuit board (PCB) that contains buses, or electrical pathways, that interconnect electronic components. These components may be soldered directly to the motherboard, or added using sockets, expansion slots, and ports.

Complete 1.2.2.2 Motherboard Components1.2.2.2 Motherboard Components

These are some connections on the motherboard where computer components can be added, as shown in the figure of a motherboard below.

asset.descriptionasset.descriptionRAM SlotsInternal USBChipsetBIOS/UEFI ChipExpansion SlotsCPU SocketMotherboard Connections

The connections labeled in the figure are the following:

Central Processing Unit (CPU) - This is considered the brain of the computer.

Random Access Memory (RAM) - This is a temporary location to store data and applications

Expansion slots - These provide locations to connect additional components.

Chipset - This consists of the integrated circuits on the motherboard that control how system hardware interacts with the CPU and motherboard. It also establishes how much memory can be added to a motherboard and the type of connectors on the motherboard.

Basic input/output system (BIOS) chip and Unified Extensible Firmware Interface (UEFI) chip - BIOS is used to help boot the computer and manage the flow of data between the hard drive, video card, keyboard, mouse, and more. In modern computers BIOS has been replaced by UEFI. UEFI specifies a different firmware for boot and runtime services. Firmware is programming that allows a computer operating system to control the hardware.

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Select the arrows below for more information on some additional important connectors

SATA

SATA, or Serial Advanced Technology Attachment (ATA), is a disk drive interface used for connecting optical drives, hard drives, and solid-state drives to the motherboard. SATA supports hot swapping, which is the ability to replace devices without powering off the computer.

Complete 1.2.2.3 Motherboard Chipset1.2.2.3 Motherboard Chipset

The figure illustrates how a motherboard connects various components.

Most chipsets consist of the following two types:

Northbridge – Controls high speed access to the RAM and video card. It also controls the speed at which the CPU communicates with all of the other components in the computer. Video capability is sometimes integrated into the Northbridge.

Southbridge – Allows the CPU to communicate with slower speed devices including hard drives, Universal Serial Bus (USB) ports, and expansion slots

This image displays the topology for the motherboard chipset. The two types of chipsets (Northbridge and Southbridge) are connected to each other. Northbridge: Connected at the top is the PCI express graphics adapter slot. On the left side of the Northbridge the CPU is connected. At the bottom portion of the Northbridge are four sticks of RAM. Southbridge: Connected at the top are the hard drives. Connected at the right are PCI adapter slots. There are two 32-bit PCI slots and two 64-bit PCI slots. Connected to the bottom of the Southbridge is the BIOS UEFI which is connected horizontally to the keyboard mouse USB.

asset.descriptionMotherboard Component ConnectionsPCI Express Graphics Adapter SlotHard DrivesPCI Adapter Slots32-bit PCI slot32-bit PCI slot64-bit PCI slot64-bit PCI slotRAMRAMRAMRAMBIOS UEFIKeyboard Mouse USBCPUNorthbridgeSouthbridge

Complete 1.2.2.4 Motherboard Form Factors1.2.2.4 Motherboard Form Factors

The form factor of motherboards pertains to the size and shape of the board. It also describes the physical layout of the different components and devices on the motherboard.

There have been many variations of motherboards developed over the years. There are three common motherboard form factors:

Advanced Technology eXtended (ATX) - This is the most common motherboard form factor. The ATX case accommodates the integrated I/O ports on the standard ATX motherboard. The ATX power supply connects to the motherboard via a single 20-pin connector.

Micro-ATX – This is a smaller form factor that is designed to be backward-compatible with ATX. Micro-ATX boards often use the same Northbridge and Southbridge chipsets and power connectors as full-size ATX boards and therefore can use many of the same components. Generally, Micro-ATX boards can fit in standard ATX cases. However, Micro-ATX motherboards are much smaller than ATX motherboards and have fewer expansion slots.

ITX - The ITX form factor has gained in popularity because of its very small size. There are many types of ITX motherboards; however, Mini-ITX is one of the most popular. The Mini-ITX form factor uses very little power, so fans are not needed to keep it cool. A Mini-ITX motherboard has only one PCI slot for expansion cards. A computer based on a Mini-ITX form factor can be used in places where it is inconvenient to have a large or noisy computer.

The table highlights these and other form factor variations.

Note: It is important to distinguish between form factors. The choice of motherboard form factor determines how individual components attach to it, the type of power supply required, and the shape of the computer case. Some manufacturers also have proprietary form factors based on the ATX design. This causes some motherboards, power supplies, and other components to be incompatible with standard ATX cases.

Complete 1.2.2.4-table-0Motherboard Form Factors

Incomplete 1.2.2.5 Check Your Understanding - Motherboards1.2.2.5 Check Your Understanding - Motherboards

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Incomplete 1.2.3 CPUs and Cooling Systems1.2.3 CPUs and Cooling Systems

Complete 1.2.3.1 What is a CPU?1.2.3.1 What is a CPU?

The central processing unit (CPU) is responsible for interpreting and executing commands. It handles instructions from the computer's other hardware, such as a keyboard, and software. The CPU interprets the instructions and outputs the information to the monitor or performs the requested tasks.

The CPU is a small microchip that resides within a CPU package. The CPU package is often referred to as the CPU. CPU packages come in different form factors, each style requiring a particular socket on the motherboard. Common CPU manufacturers include Intel and AMD.

The CPU socket is the connection between the motherboard and the processor. Modern CPU sockets and processor packages are built around the following architectures:

Pin Grid Array (PGA)

In PGA architecture (shown below), the pins are on the underside of the processor package and is inserted into the motherboard CPU socket using zero insertion force (ZIF). ZIF refers to the amount of force needed to install a CPU into the motherboard socket or slot.

Land Grid Array (LGA)

In an LGA architecture (shown below), the pins are in the socket instead of on the processor.

Complete 1.2.3.2 Cooling Systems1.2.3.2 Cooling Systems

The flow of current between electronic components generates heat. Computer components perform better when kept cool. If the heat is not removed, the computer may run more slowly. If too much heat builds up, the computer could crash, or components can be damaged. Therefore, it is imperative that computers be kept cool.

Computers are kept cool using active and passive cooling solutions. Active solutions require power while passive solutions do not. Passive solutions for cooling usually involve reducing the speed at which a component is operating or adding heat sinks to computer chips. A case fan is considered as active cooling. The figure shows examples of passive and active cooling solutions.

Heat Sink (Passive Cooling)

Heat Sink (Passive Cooling)

Case Fan (Active Cooling)

Incomplete 1.2.3.3 Check Your Understanding - CPUs and Cooling Systems1.2.3.3 Check Your Understanding - CPUs and Cooling Systems

Incomplete Question 1Question 1

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True or False.

In LGA architecture, the pins are on the underside of the processor which is inserted into the motherboard CPU socket using ZIF.

true

false

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Incomplete Question2Question2

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What is an example of passive cooling for CPU?

case fan

Land Grid Array

heat sink

Pin Grid Array

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Incomplete 1.2.4 Memory1.2.4 Memory

Complete 1.2.4.1 Types of Memory1.2.4.1 Types of Memory

A computer might use different types of memory chips, as shown in the figure. However, all memory chips store data in the form of bytes. A byte is a grouping of digital information and represents information such as letters, numbers, and symbols. Specifically, a byte is a block of eight bits stored as either 0 or 1 in the memory chip.

Read-Only Memory

An essential computer chip is the read-only memory (ROM) chip. ROM chips are located on the motherboard and other circuit boards and contain instructions that can be directly accessed by a CPU. The instructions stored in ROM include basic operation instructions such as booting the computer and loading the operating system.

ROM is nonvolatile which means that the contents are not erased when the computer is powered off.

Random Access Memory

RAM is the temporary working storage for data and programs that are being accessed by the CPU. Unlike ROM, RAM is volatile memory, which means that the contents are erased every time the computer is powered off.

Adding more RAM in a computer enhances the system performance. For instance, more RAM increases the memory capacity of the computer to hold and process programs and files. With less RAM, a computer must swap data between RAM and the much slower hard drive. The maximum amount of RAM that can be installed is limited by the motherboard.

Incomplete 1.2.4.2 Types of ROM1.2.4.2 Types of ROM

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Select the arrows to learn more about different types of ROM.

ROM

Read-only memory chips. Information is written to a ROM chip when it is manufactured. A ROM chip that cannot be erased or re-written is now obsolete. The term ROM still tends to be used generically for any read-only memory chip type.

Incomplete 1.2.4.3 Types of RAM1.2.4.3 Types of RAM

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Select each type of RAM to learn more information.

Dynamic RAM

Static RAM

SDRAM

Double Data Rate Synchronous Dynamic RAM

DDR2 Synchronous Dynamic RAM

DDR3 Synchronous Dynamic RAM

DDR4 Synchronous Dynamic RAM

GDDR Synchronous Dynamic RAM

DDR5

Incomplete 1.2.4.4 Memory Modules1.2.4.4 Memory Modules

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Early computers had RAM installed on the motherboard as individual chips. The individual memory chips, called dual inline package (DIP) chips, were difficult to install and often became loose. To solve this problem, designers soldered the memory chips to a circuit board to create a memory module which would then be placed into a memory slot on the motherboard.

Select the arrows to learn more about different types of memory modules.

DIP

Dual Inline Package is an individual memory chip. A DIP has dual rows of pins used to attach it to the motherboard.

Complete Single-Sided, Double-Sided, and Multi-channelSingle-Sided, Double-Sided, and Multi-channel

Memory modules can be single-sided or double-sided. Single-sided memory modules contain RAM on only one side of the module. Double-sided memory modules contain RAM on both sides.

The speed of memory has a direct impact on how much data a processor can process in a given period of time. As processor speed increases, memory speed must also increase. Memory throughput has also been increased through multichannel technology. Standard RAM is single channel, meaning that all of the RAM slots are addressed at the same time. Dual channel RAM adds a second channel to be able to access a second module at the same time.

Triple channel technology provides another channel so that three modules can be accessed at the same time. Quadruple channel adds another channel to the memory controller for even higher bandwidth. To use triple and quadruple channel memory controllers for the most bandwidth, the chipset architecture must support it and will only be able to use as many channels that have memory slots populated. In many cases, memory slots can only be populated in a certain order in order to ensure all memory channels are used.

Incomplete Cache MemoryCache Memory

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The fastest memory is typically static RAM (SRAM) which is cache memory for storing the most recently used data and instructions by the CPU. SRAM provides the processor with faster access to the data than retrieving it from the slower dynamic RAM (DRAM), or main memory.

Select each type of cache memory to learn more.

L1

L1 cache is internal cache and is integrated into the CPU. A CPU can have various models each with a different amount of L1 cache.

L1

L2

L3

Incomplete Memory ErrorsMemory Errors

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Memory errors occur when the data is not stored correctly in the chips. The computer uses different methods to detect and correct data errors in memory.

Select each type of error checking method to learn more.

Nonparity

Nonparity memory does not check for errors in memory. Nonparity RAM is the most common RAM used for home and business workstations.

Nonparity

Parity

ECC

Incomplete 1.2.4.5 Check Your Understanding: Memory1.2.4.5 Check Your Understanding: Memory

Incomplete Question 1Question 1

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Which statement describes EPROM?

It is a type of RAM

It is a type of volatile memory

It can only be programmed once

Data can be erased using a strong ultraviolet light

Data is programmed on it when it is manufactured

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Incomplete Question 2Question 2

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A user complains that the computer is running very slowly. What solution would help speed it up?

Add more RAM

Add more ROM

Switch to L1 cache

Use error correction code memory

Erase and refresh the code in ROM

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Incomplete Question 3Question 3

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Which RAM in the group provides the fastest performance?

GDDR SDRAM

SDRAM