1.2 PC Components
1.2.1 Case and power supplies
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:
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.
188.8.131.52 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.
A power supply includes several different connectors, as shown in 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.
184.108.40.206 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.
220.127.116.11 Check Your Understanding - Cases and Power Supplies
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.
18.104.22.168 Motherboard Components
These are some connections on the motherboard where computer components can be added, as shown in the Figure 1:
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. Recently the BIOS has been enhanced by UEFI. UEFI specifies a different software interface for boot and runtime services but still relies on the traditional BIOS for system configuration, power-on self -test (POST), and setup.
Some additional important connectors are shown in Figure 2.
22.214.171.124 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
126.96.36.199 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 in the figure highlights these and other form factor variations.
188.8.131.52 Check Your Understanding - Motherboards
1.2.3 CPUs and Cooling Systems
184.108.40.206 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) - (Figure 1) In PGA architecture, 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) - (Figure 2) In an LGA architecture, the pins are in the socket instead of on the processor.
220.127.116.11 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.
18.104.22.168 Check Your Understanding - CPUs and Cooling Systems
22.214.171.124 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.
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.
126.96.36.199 Types of ROM
188.8.131.52 Types of RAM
184.108.40.206 Memory Modules
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.
The different types of memory modules are described in Figure 1.
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.
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.
The three most common types of cache memory are described in Figure 2.
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.
Different types of error checking methods are described in Figure 3.
220.127.116.11 Check Your Understanding - Memory
1.2.5 Adapter Cards and Expansion Slots
18.104.22.168 Adapter Cards
Adapter cards increase the functionality of a computer by adding controllers for specific devices or by replacing malfunctioning ports.
There are a variety of adapter cards available that are used to expand and customize the capability of a computer:
Sound adapter - Sound adapters provide audio capability.
Network Interface Card (NIC) - A NIC connects a computer to a network using a network cable.
Wireless NIC - A wireless NIC connects a computer to a network using radio frequencies.
Video adapter - Video adapters provide video capability.
Capture card - Capture cards send a video signal to a computer so that the signal can be recorded to a storage drive with video capture software.
TV tuner card - These provide the ability to watch and record television signals on a PC by connecting a cable television, satellite, or antenna to the installed tuner card.
Universal Serial Bus (USB) controller card - Provides additional USB ports to connect the computer to peripheral devices.
eSATA card - Adds additional internal and external SATA ports to a computer through a single PCI Express slot.
Figure 1 shows some of these adapter cards. It should be noted that some of these adapter cards can be integrated on the motherboard.
Computers have expansion slots on the motherboard to install adapter cards. The type of adapter card connector must match the expansion slot. Refer to Figure 2 to learn about expansion slots.
22.214.171.124 Check Your Understanding - Adapter Cards and Expansion Slots
1.2.6 Hard disk drives and SSDs
126.96.36.199 Types of Storage Devices
A number of different types of devices are available for data storage on a PC, as shown in the figure. Data drives provide non-volatile storage of data, meaning that when the drive loses power, the data is retained and available the next time the drive is powered on. Some drives have fixed media, and other drives have removable media. Some offer the ability to read and write data, while others only allow data to be accessed, but not written. Data storage devices can be classified according to the media on which the data is stored; magnetic like HDD and tape drives, solid state, or optical.
188.8.131.52 Storage Device Interfaces
Internal storage devices often connect to the motherboard using Serial AT Attachment (SATA) connections. The SATA standards define the way that data is transferred, the transfer rates, and physical characteristics of the cables and connectors.
There are three main versions of the SATA standard: SATA 1, SATA 2, and SATA 3, as shown in the figure. The cables and connectors are the same, but the data transfer speeds are different. SATA 1 allows for a maximum data transfer rate of 1.5 Gb/s while SATA 2 can reach up to 3 Gb/s. SATA 3 is the fastest with speeds up to 6 Gb/s.
Small Computer System Interface (SCSI) is another interface between motherboards and data storage devices. It is an older standard that originally used parallel, rather than serial, data transfers. A new version of SCSI known as Serially Attached SCSI (SAS) has been developed. SAS is a popular interface used for server storage.
184.108.40.206 Magnetic Media Storage
One type of storage represents binary values as magnetized or non-magnetized physical areas of magnetic media. Mechanical systems are used to position and read the media. The following are common types of magnetic media storage drives:
Hard Disk Drive (HDD) - HDDs are the traditional magnetic disk devices that have been used for years. Their storage capacity ranges from gigabytes (GBs) to terabytes (TBs). Their speed is measured in revolutions per minute (RPM). This indicates how fast the spindle turns the platters that hold the data. The faster the spindle speed, the faster a hard drive can find data on the platters. This can correspond to faster transfer speeds. Common hard drive spindle speeds include 5400, 7200, 10,000, and 15,000 RPM. HDDs come in 1.8, 2.5 and 3.5 inch form factors, as shown in Figure 1. The 3.5 inch form factor is standard for personal computers. 2.5 inch HDDs are typically used in mobile devices. 1.8 inch HDDs were used in portable media players and other mobile applications, but are seldom used in new devices.
Tape Drive - Magnetic tapes are most often used for archiving data. At one time they were useful for backing up PCs, however as HDDs became cheaper, external HDD drives are now frequently used for this purpose. However, tape backups are still used in enterprise networks. Tape drives use a magnetic read/write head and removable tape cartridge, as shown in Figure 2. Although data retrieval using a tape drive can be fast, locating specific data is slow because the tape must be wound on a reel until the data is found. Common tape storage capacities vary between a few GBs to many TBs.
220.127.116.11 Semiconductor Storage
Solid-state drives (SSD) store data as electrical charges in semiconductor flash memory. This makes SSDs much faster than magnetic HDDs. SSD storage capacity ranges from around 120 GBs to many TBs. SSDs have no moving parts, make no noise, are more energy efficient, and produce less heat than HDDs. Because SSDs have no moving parts to fail, they are considered to be more reliable than HDDs.
SSDs come in three form factors:
Disc drive form factor - These are similar to an HDD in which the semiconductor memory is in a closed package that can be mounted in computer cases like an HDD. They can be 2.5, 3.5, and 1.8 inches, although those are rare.
Expansion cards - This plugs directly into the motherboard and mounts in the computer case like other expansion cards.
mSata or M.2 modules - These packages may use a special socket. M.2 is a standard for computer expansion cards. It is a family of standards that specify physical aspects of expansion cards such as connectors and dimension.
These form factors are shown in Figure 1. Figure 2 shows the 2.5 inch and M.2 form factors in comparison to a 3.5 inch magnetic HDD.
The Non-Volatile Memory Express (NVMe) specification was developed specifically to allow computers to take greater advantage of the features of SSDs by providing a standard interface between SSDs, the PCIe bus, and operating systems. NVMe allows compliant SSD drives to attach to the PCIe bus without requiring special drivers, in much the same way that USB flash drives can be used in multiple computers without requiring installation on each.
Finally, Solid State Hybrid Drives (SSHDs) are a compromise between a magnetic HDD and an SSD. They are faster than an HDD but less expensive than an SSD. They combine a magnetic HDD with onboard flash memory serving as a non-volatile cache. The SSHD drive automatically caches data that is frequently accessed, which can speed up certain operations such as operating system start up.
18.104.22.168 Check Your Understanding - Data Storage Devices
1.2.7 Optical Storage Devices
22.214.171.124 Types of Optical Storage Devices
Optical drives are a type of removable media storage device that use lasers to read and write data on optical media. They were developed to overcome the storage capacity limitations of removable magnetic media such as floppy discs and magnetic storage cartridges. Figure 1 shows an internal optical drive. There are three types of optical drives:
Compact Disc (CD) - audio and data
Digital Versatile Disc (DVD) - digital video and data
Blu-ray Disc (BD) - HD digital video and data
CD, DVD, and BD media can be pre-recorded (read only), recordable (write once), or re-recordable (read and write multiple times). DVD and BD media can also be single layer (SL) or dual layer (DL). Dual layer media roughly doubles the capacity of a single disc.
Figure 2 describes the various types of optical media and their approximate storage capacities.
126.96.36.199 Check Your Understanding - Types of Optical Media
1.2.8 Ports, Cables, and Adaptors
188.8.131.52 Video Ports and Cables
A video port connects a monitor cable to a computer. Video ports and monitor cables transfer analog signals, digital signals, or both. Computers are digital devices that create digital signals. The digital signals are sent to the graphics card where they are transmitted through a cable to a display.
184.108.40.206 Other Ports and Cables
Input/output (I/O) ports on a computer connect peripheral devices such as printers, scanners, and portable drives. In addition to the ports and interfaces previously discussed, a computer may also have other ports.
220.127.116.11 Adapters and Converters
There are many connection standards in use today. Many are interoperable but require specialized components. These components are called adapters and converters:
Adapter - This is a component that physically connects one technology to another. For example, a DVI to HDMI adapter. The adapter could be one component or a cable with different ends.
Converter - This performs the same function as an adapter but also translates the signals from one technology to the other. For example, a USB 3.0 to SATA converter enables a hard disk drive to be used as a flash drive.
18.104.22.168 Check Your Understanding - Cables and Connectors
1.2.9 Input Devices
22.214.171.124 The Original Input Devices
Input devices allow the user to communicate with a computer. The images below are some of the first input devices.
126.96.36.199 New Input Devices
Some new input devices include touch screen, a stylus, a magnetic strip reader and a barcode scanner.
188.8.131.52 More New Input Devices
184.108.40.206 Most Recent Input Devices
The newest input devices include NFC devices and terminals, facial recognition scanners, fingerprint scanners, voice recognition scanners, and virtual reality headsets.
220.127.116.11 Check Your Understanding - Input Devices
1.2.10 Output Devices
18.104.22.168 What are Output Devices?
An output device takes binary information (ones and zeroes) from the computer and converts it into a form that is easily understood by the user.
Monitors and projectors are output devices that create visual and audio signals for the user (Figure 1). Virtual Reality (VR) headsets are another type of output device. Televisions may also be output devices. Printers are visual output devices that create hard copies of computer files.
Speakers and headphones are output devices that produce only audio signals (Figure 2). Output devices make it possible for users to interact with computers.
22.214.171.124 Monitors and Projectors
126.96.36.199 VR and AR Headsets
Virtual Reality (VR) uses computer technology to create a simulated, three-dimensional environment. The user feels immersed in this ‘virtual world’ and manipulates it. A VR headset completely encases the upper portion of users’ faces, not allowing in any ambient light from their surroundings. Most VR experiences have three-dimensional images that seem life-sized to the user. VR experiences also track a user’s motions, and adjust the images on the user’s display accordingly.
Augmented Reality (AR) uses similar technology but superimposes images and audio over the real world in real time. AR can provide users with immediate access to information about their real surroundings. An AR headset usually does not close off ambient light to users, allowing them to see their real life surroundings. Not all AR requires a headset. Some AR can simply be downloaded onto a smart phone. Pokemon GO is an early version of an AR game that uses a player’s smart phone to ‘see and capture’ virtual objects in the real world. Other AR devices are smart glasses. They weigh much less than the headsets and are often designed for a specific audience, such as cyclists.
Printers are output devices that create hard copies of files. A hard copy might be a on a sheet of paper. It could also be a plastic form created from a 3D printer.
The figure shows a variety of printer types. Today’s printers may be wired, wireless, or both. They use different technology to create the image you see. All printers require printing material (such as ink, toner, liquid plastic, etc.) and a method to place it accurately on the paper or extrude it into the desired shape. All printers have hardware that must be maintained. Most printers also have software, in the form of drivers that must be kept up to date.