Internal Components

Explains the most important internal components of desktop computers. Processing, memory, storage, and communication.

Published

September 10, 2024

Modified

August 8, 2025

The major internal components of desktop computers. Image source: TBA

The major internal components of desktop computers. Image source: TBA

Introduction

In previous weeks we learned the basic behaviors that define computers – their ability to store, retrieve, and process information. This means that many simple devices, even non-electronics, can be considered computers.

The computers that we mostly are concerned with in the computer science profession, however, are generally complicated electronic devices made of many components. In this class, we are going to learn many of the fundamental components that make up modern computing devices.

We will continue with the internal, or system, components of a computer – each of these have their own set of interesting behaviors and properties that are worth understanding.

Lesson overview

The system components of a computer are responsible for the following behaviors:

  • Main needs:
    • store information
    • process information
    • retrieve information
  • Auxiliary needs:
    • protection from elements/interference
    • source of electrical power
    • temperature management for heat generated
    • structure
    • communication between components
    • tiers of storage/processing specialized for different purposes

Here are system components that fulfil these needs:

  • Case
  • Power Supply
  • Motherboard
    • Chipset
    • Buses
  • Connectors
  • Cooling Devices
  • Processor (CPU)
  • Graphics processor (GPU)
  • Memory (RAM)
  • Storage Devices (CD, HDD, SSD, NVME/M2)

We will learn about all of these components this week!

Definitions

When discussing components of any complicated machine, we should try to understand the following about those components:

Make/model

Make/model is the brand and product name of the component. * E.g. Hyundai Accent (make = Hyundai, model = Accent)

Why it’s important: Who constructs these components? Are their multiple different versions of this component made by the same manufacturer? Why?

Properties

Properties are the quantitative (numeric) and qualitative (non-numeric) traits of the component that can be compared with alike components * Quantitative e.g.: the Fuel Efficiency of the 2009 Hyundai Accent is 29 MPG (miles per gallon) * Qualitative e.g: The Hyundai Accent is a hatchback, not a sedan

Why it’s important: * what is the expected performance of this component? * Is their a cost/benefit for choosing a component with better suited properties than other components? * Etc.

These two ideas (make/model, properties) will vary significantly from component to component. You will need to know these ideas for all of the components we discuss today.

Case

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  • Provides protection and cooling for the internal components.
  • Also prevents damage from static electricity (components grounded via attachment to case).
  • Usually made of plastic, steel or aluminum.
  • Fans move air through the case:
    • to replace warm air with cold air to keep components at stable temperatures
    • to prevent build-up of dust
    • There exist many guides/studies for optimal airflow. E.g. https://voltcave.com/pc-airflow-guide/

Power Supply (PSU)

Main purpose:  Converts AC power (alternating current) from wall socket to DC power (direct current). Direct current (0 or 5V) is used to power digital circuits.

  • Note: PSU have their own fans: Energy conversion releases a lot of heat!
  • Computers can only tolerate slight fluctuations in power without needing to shut down
  • Important: Never open a power supply! The capacitors contained within can keep a dangerous high voltage, high power charge long after being unplugged.

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PSU Connectors

  • Most power supply connectors are : 20 + 4 pins
  • Usually made up of wires of various colors:
    • Yellow 12V
    • Red 5V
    • Orange 3.3V
    • Other colors may be ground 0V

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PSU Ratings

Useful for Assignment 1

PSU Ratings: * Wattage (amount of power delivered, must be greater than the sum of power required by all parts, some power supplies can provide more power than others) * Efficiency (1st + 2nd Laws of thermodynamics: 100% power input cannot be converted to 100% power output; some power supplies have higher efficiency ratings than others) * For more detailed explanation:  https://www.newegg.com/insider/how-to-choose-a-pc-power-supply-buying-guide/

Uninterruptible Power Supply

In the case of a power outage, an Uninterruptible Power Supply (UPS) can keep a computer running for a few minutes to several hours depending on the sophistication of the UPS. See  https://www.wikihow.com/Buy-and-Use-an-Uninterruptible-Power-Supply  for an example.

It’s basically a large battery that keeps charge during normal operation, and powers a computer using its stored charge when the building’s power is cut off.

We will talk more about uninterruptible power supply when we start speaking about server hardware.

Motherboard

Motherboards connect all the major components of the computer: the CPU, RAM, Expansion ports, etc.

An ASUS Pro B660M Motherboard. Most motherboards look something like this.

An ASUS Pro B660M Motherboard. Most motherboards look something like this.
  • Composed of various chips all combined into north and south  bridges
  • Main circuit board and controls the electrical pathways (buses) found in a computer.
  • The buses allow data to travel between the various components of a computer.
  • Various form factors, e.g. AT, ATX, LPX, BTX, ITX.

Motherboard form factors, from largest to smallest.

Motherboard form factors, from largest to smallest.

Form Factors

  • AT
    • Invented by IBM in early 1980s, now obsolete.
    • Huge in size (approximately 12 x 13 inches).
    • Needed lots of space for power supply and its various chips.
    • Lacked external ports, only allowed for monitor and keyboard.
  • ATX
    • Created in 1995 to meet the need for more connectors.
    • Got off to a slow start but by 1998 became the most common form factor.
    • Biggest change to AT was the rear panel with standard set of ports for expansion.
    • Power supply position for better airflow, CPU and RAM positioned for easier access.
    • Variations 12x9in (full size), 9.6x9.6in ( microATX )
  • ATX and microATX are the most common in personal desktop computers today
  • ITX
    • Created in 2001 to meet the demand for smaller computers.
    • ITX failed but led to development of smaller form factor (SSF) motherboards.
    • MiniITX (6.7x6.7in), NanoITX (4.7x4.7in) and PicoITX (3.8x2.8in)
    • Commonly used for embedded systems and specialized devices such as routers.
    • Require very little power, therefore produce less heat.
  • Proprietary
    • Some computer manufacturers make motherboards that work only with their cases.
    • Services and upgrades usually need to be handled by authorized dealers.
    • Often hard to get replacement parts and they are usually expensive.

I/O Ports

You’ll notice that the I/O Ports (input/output) on the mother board are always located around the same area.

This is to keep certain consistency across manufacturer and regardless of the form factors

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Expansion Slots

Let’s have a closer look at what we call expansion slots.

Expansion slots are ports inside a computer found on the motherboard. They provide the possibility to expand the hardware of your PC.

For example, you may want to install a network card, a sound card, and most commonly, a video card.

Expansion slots allow us to increase the functionality of a computer by adding controllers for specific devices (often called adapter cards) e.g. sound, video, NIC (network Interface Card).

  • PCI used in most computers, commonly used for network interface
  • AGP designed to be used by video adapters
  • PCIe replaces AGP in newer computers, used for video cards
  • ISA older, rarely used, 8 or 16 bit
  • EISA older, rarely used, 32 bit
  • MCA IBM proprietary 32 bit, older, rarely used
  • PCI-X 32 bit, can run up to four times faster than PCI
  • MiniPCI 32 bit, used by laptops, has three different form factors

In 2024 : PCI and PCIe are the common standards that cover all features required for expansion slots

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CPU Socket

Let’s have a closer look at the CPU Socket, which rests in the motherboard. This is where the CPU will sit.

The motherboard…

The motherboard…

… and the CPU socket.

… and the CPU socket.

How to Connect a CPU?

CPU connection on the motherboard is known as the CPU socket.

The CPU is connected to the motherboard in one of two ways:

  • Pin Grid Array – PGA
    • Pins are on the CPU (underside of the processor).
    • Socket on motherboard includes holes that line up with the CPU pins.
  • Land Grid Array – LGA
    • Pins are on the motherboard (on socket) instead of on the processor.

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Internal Connectors

There are a variety of connectors used to connect components to the motherboard. Two main purposes:

  • Signals : for communication/data transfer
  • Power : not all components connect directly to the power supply, they get power from the motherboard

Most connectors are keyed (can only be inserted one way). Note: Always check the pins if you have trouble with a connector.

“If it doesn’t go in like butter, it doesn’t go in at all” – never force a connection! you are likely going to damage the pins.

Example connectors

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CPU

The CPU Most important element of the computer.

  • Responsible for interpreting and executing the commands from the software.
  • communicates instructions for all of the other components of the computer
  • While the CPU is processing one step of the program, the remaining instructions and the data are stored in a special memory called cache.

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We’ll have a lecture dedicated to the CPU since it is so complicated.

CPU Brands

Intel: Historically the main CPU manufacturer

AMD: Relatively recent competitor to Intel

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Cooling Devices

The flow of current between and within electronic components generates heat. Some devices are particularly powerful heat-generators, due to the large current they draw: * CPUs typically come with their own cooling device * Cooling devices are built into GPUs and Power Supplies

There are two main types of cooling devices:

  • Fans inside the case increase airflow and removes heat.
  • Heat sinks also draw heat away from the CPU core.

Fans

The flow of current between the electronic components generates heat.

Fans inside the case increase airflow and removes heat.

Occasionally video cards or other components have their own fans to cool them.

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Heat sinks

  • Heat sinks also draw heat away from the CPU core.
    • A heat sink is a piece of copper or aluminum that resides between the processor and the CPU fan.
    • It absorbs the heat from the processor and the fan disperses the heat.

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Main Memory (RAM)

Referred to as RAM (Random Access Memory). They’re connected to RAM slots on the motherboard:

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RAM is a collection of integrated circuits (chips). Temporary storage for data and programs that are being accessed by the CPU.

Volatile memory : contents are erased when the computer is switched off. (or when power is lost)

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Properties

There are four main properties of RAM to know:

  • Capacity: Total memory (in GB, GigaBytes)
    • More RAM means more capacity to hold and process large programs and files.
    • Maximum installed is limited by the motherboard and the operating system.
  • Speed: How many operations per second
    • Many, millions or billions per second
    • 1MHz = 1 million / second, 1 GHz = 1 billion / second
  • Latency : How much time delay between communications
  • Generation: See next slides

RAM Form Factors

  • SIMMs (Single In-Line Memory Modules)
    • Have a single line of connectors.
    • Now obsolete.
  • DIMMs (Dual In-Line Memory Modules)
    • Have two lines of connectors.
    • Have Wider bus (supports 64 bits) 🡪 How can this help? More on this in the coming weeks.
    • Became dominant (no need to state that a memory module is a DIMM).

RAM Generations

Synchronous DRAM (SDRAM) DRAM that operates in time with the memory bus.
Tied to the system clock like the CPU and the memory controller.
Results in very little wasted time.
Double Data Rate SDRAM (DDR) DDR transfers data twice as fast as SDRAM. Larger buffer gives it a huge boost.
Double Data Rate 2 SDRAM (DDR2) DDR2 decreases noise making it faster than DDR.
Double Data Rate 3 SDRAM (DDR3) DDR3 doubles the clock rate of DDR2, consumes less power and generates less heat.
Double Data Rate 4 SDRAM (DDR4) DDR4 arrived in 2014 with even faster speeds. (most common RAM type in desktops/laptops today)
Double Data Rate 5 SDRAM (DDR5) Introduced in 2020, is starting to become more widely adopted.

NOTE: Motherboards are usually compatible with only ONE generation of RAM. If you have a motherboard designed for DDR3, it cannot use DDR4 or DDR5.

Graphics Cards (GPU)

Also known as Video cards or Graphical Processing Units

One of the most interesting use of expansion slots is the addition of video cards, also known as Graphical Processing Unit.

A specialized version of a CPU designed for graphical processing (producing complex output to display on a monitor)

The computation needed for graphical processing is generally useful for scientific computing as well (lots of data in parallel)

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CPU vs GPU

  • Both consume a lot of power and generate a lot of heat
  • More powerful CPUs/GPUs require more powerful power supplies
    • TDP: __ Thermal Design Power, measures the number of Watts needed to power the device__
  • Both have performance measured in speed __ (operations/second) like RAM__

GPU cannot replace the CPU because their architecture is different and meant for different purposes. GPU is great to parallelize computations! But the GPU is not as versatile as the CPU which has a larger instruction set

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Storage Devices

Storage devices store data permanently. Some are installed inside the case (e.g. hard drive); Some are removable and portable (e.g. external flash drive).

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Floppy Drive

Uses 3.5 inch floppy disks (or 5.25 inch floppy disks - older).

Largely obsolete.

Magnetic disks store up to 1.44Meg of data.

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Hard Drive

  • Hard Disk Drive (HDD)
    • Traditional hard drives.
    • Uses magnetic-based storage on a moving disk (somewhat like a vinyl player)
    • Magnetic hard drives have drive motors that spin the magnetic platters and move the drive heads.
    • Speed measured in revolutions per minute

  • Solid State Drives (SSD)
    • Do not have moving parts and use __ semi-conductors__ to store data.
    • Non-volatile flash memory chips manage the storage on an SSD, resulting in faster access to data, higher reliability and reduced power usage.

Tape Drive

Magnetic tapes are often used for backups or archiving data. Impractical for most individuals, but still used/created to this day! Cost effective when storing more than 1000 TB (lots and lots of data)

Optical Drive

  • Uses lasers to read the data on the optical media.
    • CD (compact disc) 700 Mb
    • DVD (digital versatile disc) 4-8 Gb.
    • BD (Blu-ray disc) 25-50 Gb.
  • Optical media can be:
    • Pre-recorded (read only)
    • Recordable (write once)
    • Re-recordable (read and write multiple times).

Interfaces Types

Interface Types, in order of oldest to newest

IDE
 		 Integrated Drive Electronics / Advanced Technology Attachment.
Also called ATA.
Early drive controller interface, originally only supported hard drives up to 540 MB.
Uses a 40 pin connector, and maximum cable length of 46cm (18in).
EIDE Enhanced Integrated Drive Electronics (also called ATA-2).
Updated version of IDE, supporting larger drives and direct memory access.
Uses a 40 pin connector.
PATA Parallel version of ATA.
Used internally due to maximum cable length of 46cm (18in).
Largely replaced by SATA in newer systems.
SATA (most commonly used today) Serial version of ATA, with slimmer and longer cables providing better airflow.
Uses 7-pin connector (less pins means less issues with electromagnetic interference).
SATA hard drives tend to be quieter than IDE drives.
eSATA External serial ATA, provides a hot-swappable external interface for SATA.
:-: :-:
SCSI Small Computer System Interface.
Drive controller that can connect up to 15 drives.
Internal and external use, uses 25, 50 or 68 pin connector.

Note: __ Hot-swapping is the ability to connect and disconnect a device while the computer is on.__

External Flash Drive

Removable storage device that connects to a USB port.

These use the same type of non-volatile memory chips as SSDs and do not require power to maintain the data.

To install a drive internally in a computer, the connection interface on the drive must be the same as the controller on the motherboard.

Motherboards support different types of interfaces.

Computer Memory Hierarchy

Source: https://en.wikipedia.org/wiki/Memory_hierarchy

Exercises

Knowledge check

Additional resources

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