Computer hardware

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PDP-11 CPU board PDP-11-M7270.jpg
PDP-11 CPU board

Computer hardware includes the physical parts of a computer, such as the case, [1] central processing unit (CPU), monitor, keyboard, computer data storage, graphics card, sound card, speakers and motherboard. [2]

Contents

By contrast, software is the set of instructions that can be stored and run by hardware. Hardware is so-termed because it is "hard" or rigid with respect to changes, whereas software is "soft" because it is easy to change.

Hardware is typically directed by the software to execute any command or instruction. A combination of hardware and software forms a usable computing system, although other systems exist with only hardware.

Von Neumann architecture

Von Neumann architecture scheme Von Neumann Architecture.svg
Von Neumann architecture scheme

The template for all modern computers is the Von Neumann architecture, detailed in a 1945 paper by Hungarian mathematician John von Neumann. This describes a design architecture for an electronic digital computer with subdivisions of a processing unit consisting of an arithmetic logic unit and processor registers, a control unit containing an instruction register and program counter, a memory to store both data and instructions, external mass storage, and input and output mechanisms. [3] The meaning of the term has evolved to mean a stored-program computer in which an instruction fetch and a data operation cannot occur at the same time because they share a common bus. This is referred to as the Von Neumann bottleneck and often limits the performance of the system. [4]

Types of computer systems

Personal computer

Basic hardware components of a modern personal computer, including a monitor, a motherboard, a CPU, a RAM, two expansion cards, a power supply, an optical disc drive, a hard disk drive, a keyboard and a mouse Personal computer, exploded 6.svg
Basic hardware components of a modern personal computer, including a monitor, a motherboard, a CPU, a RAM, two expansion cards, a power supply, an optical disc drive, a hard disk drive, a keyboard and a mouse
Inside a custom-built computer: power supply at the bottom has its own cooling fan Computer from inside 018.jpg
Inside a custom-built computer: power supply at the bottom has its own cooling fan

The personal computer, also known as the PC, is one of the most common types of computer due to its versatility and relatively low price. Most personal computers possess a monitor, a keyboard, a mouse, and a computer case. The computer case encloses and holds all of the necessary hardware required to store and process data on the computer. The motherboard ensures that all other inner computer hardware communicates with each other. The CPU executes instructions for running computer programs. RAM is responsible for the temporary storage of data while the computer operates.

Laptops are designed for portability and are generally very similar to PCs, [1] although they may use lower-power or reduced size components, thus lower performance for a given price point. [5] Due to their portability, all units of computer hardware in a laptop are integrated within the laptop's computer case. The monitor is found in the upper cover of the laptop, and it and the laptop itself can be secured by closing the cover. Instead of a mouse, laptops usually may have a trackpad attached below the in-built keyboard.

Case

The computer case encloses and holds most of the components of the system. It provides mechanical support and protection for internal elements such as the motherboard, disk drives, and power supplies, and controls and directs the flow of cooling air over internal components. The case is also part of the system to control electromagnetic interference radiated by the computer and protects internal parts from electrostatic discharge. Large tower cases provide extra internal space for multiple disk drives or other peripherals and usually stand on the floor, while desktop cases provide less expansion room. All-in-one style designs include a video display built into the same case. Portable and laptop computers require cases that provide impact protection for the unit. A current development in laptop computers is a detachable keyboard, which allows the system to be configured as a touch-screen tablet. Hobbyists may decorate the cases with colored lights, paint, or other features, in an activity called case modding.

Power supply

A power supply unit (PSU) converts alternating current (AC) electric power to low-voltage direct current (DC) power for the internal components of the computer. Laptops are capable of running from a built-in battery, normally for a period of hours. [6] The PSU typically uses a switched-mode power supply (SMPS), with power MOSFETs (power metal–oxide–semiconductor field-effect transistors) used in the converters and regulator circuits of the SMPS. [7]

Motherboard

The motherboard is the main component of a computer. It is a board with integrated circuitry that connects the other parts of the computer including the CPU, the RAM, the disk drives (CD, DVD, hard disk, or any others) as well as any peripherals connected via the ports or the expansion slots. The integrated circuit (IC) chips in a computer typically contain billions of tiny metal–oxide–semiconductor field-effect transistors (MOSFETs). [8]

Components directly attached to or to part of the motherboard include:

Expansion cards

An expansion card in computing is a printed circuit board that can be inserted into an expansion slot of a computer motherboard or backplane to add functionality to a computer system via the expansion bus. Expansion cards can be used to obtain or expand on features not offered by the motherboard.

Storage devices

A storage device is any computing hardware and digital media that is used for storing, porting and extracting data files and objects. It can hold and store information both temporarily and permanently and can be internal or external to a computer, server or any similar computing device. Data storage is a core function and fundamental component of computers.

Fixed media

Data is stored by a computer using a variety of media. Hard disk drives (HDDs) are found in virtually all older computers, due to their high capacity and low cost, but solid-state drives (SSDs) are faster and more power efficient, although currently more expensive than hard drives in terms of dollar per gigabyte, [9] so are often found in personal computers built post-2007. [10] SSDs use flash memory, which stores data on MOS memory chips consisting of floating-gate MOSFET memory cells. Some systems may use a disk array controller for greater performance or reliability.

Removable media

To transfer data between computers, an external flash memory device (such as a memory card or USB flash drive) or optical disc (such as a CD-ROM, DVD-ROM or BD-ROM) may be used. Their usefulness depends on being readable by other systems; the majority of machines have an optical disk drive (ODD), and virtually all have at least one Universal Serial Bus (USB) port.

Input and output peripherals

Input and output devices are typically housed externally to the main computer chassis. The following are either standard or very common to many computer systems.

Input device

Input devices allow the user to enter information into the system, or control its operation. Most personal computers have a mouse and keyboard, but laptop systems typically use a touchpad instead of a mouse. Other input devices include webcams, microphones, joysticks, and image scanners.

Output device

Output devices are designed around the senses of human beings. For example, monitors display text that can be read, speakers produce sound that can be heard [11] . Such devices could include printers, speakers, monitors or a Braille embosser.

Mainframe computer

A mainframe computer is a much larger computer that typically fills a room and may cost many hundreds or thousands of times as much as a personal computer. They are designed to perform large numbers of calculations for governments and large enterprises.

An IBM System z9 mainframe Front Z9 2094.jpg
An IBM System z9 mainframe

Departmental computing

In the 1960s and 1970s, more and more departments started to use cheaper and dedicated systems for specific purposes like process control and laboratory automation. A minicomputer, or colloquially mini, is a class of smaller computers that was developed in the mid-1960's [12] [13] and sold for much less than mainframe [14] and mid-size computers from IBM and its direct competitors.

Supercomputer

A supercomputer is superficially similar to a mainframe but is instead intended for extremely demanding computational tasks. As of June 2018, the fastest supercomputer on the TOP500 supercomputer list is the Summit, in the United States, with a LINPACK benchmark score of 122.3 PFLOPS Light, by around 29 PFLOPS.

The term supercomputer does not refer to a specific technology. Rather it indicates the fastest computations available at any given time. In mid-2011, the fastest supercomputers boasted speeds exceeding one petaflop, or 1 quadrillion (10^15 or 1,000 trillion) floating-point operations per second. Supercomputers are fast but extremely costly, so they are generally used by large organizations to execute computationally demanding tasks involving large data sets. Supercomputers typically run military and scientific applications. Although costly, they are also being used for commercial applications where huge amounts of data must be analyzed. For example, large banks employ supercomputers to calculate the risks and returns of various investment strategies, and healthcare organizations use them to analyze giant databases of patient data to determine optimal treatments for various diseases and problems incurring to the country.

Hardware upgrade

When using computer hardware, an upgrade means adding new hardware to a computer that improves its performance, increases its capacity, or adds new features. For example, a user could perform a hardware upgrade to replace the hard drive with a faster one or an SSD to get a boost in performance. Also, the user could install more RAM so the computer may run more smoothly. The user could add a USB 3.0 expansion card to fully use USB 3.0 devices, or could upgrade the GPU for extra rendering power. Performing such hardware upgrades may be necessary for older computers to meet a program’s system requirements.

Sales

Global revenue from computer hardware in 2016 reached 408 billion Euros. [15]

Recycling

Re-computer.svg

Because computer parts contain hazardous materials, there is a growing movement to recycle old and outdated parts. [16] Computer hardware contain dangerous chemicals such as: lead, mercury, nickel, and cadmium. According to the EPA these e-wastes have a harmful effect on the environment unless they are disposed of properly. Making hardware requires energy, and recycling parts will reduce air pollution, water pollution, as well as greenhouse gas emissions. [17] Disposing unauthorized computer equipment is in fact illegal. Legislation makes it mandatory to recycle computers through the government approved facilities. Recycling a computer can be made easier by taking out certain reusable parts. For example, the RAM, DVD drive, the graphics card, hard drive or SSD, and other similar removable parts can be reused.

Many materials used in computer hardware can be recovered by recycling for use in future production. Reuse of tin, silicon, iron, aluminium, and a variety of plastics that are present in bulk in computers or other electronics can reduce the costs of constructing new systems. Components frequently contain copper, gold, tantalum, [18] [19] silver, platinum, palladium, and lead as well as other valuable materials suitable for reclamation. [20] [21] [22]

Toxic computer components

The central processing unit contains many toxic materials. It contains lead and chromium in the metal plates. Resistors, semi-conductors, infrared detectors, stabilizers, cables, and wires contain cadmium. The circuit boards in a computer contain mercury, and chromium. [23] When these types of materials, and chemicals are disposed improperly will become hazardous for the environment.

Environmental effects

According to the United States Environmental Protection Agency only around 15% of the e-waste actually is recycled. When e-waste byproducts leach into groundwater, are burned, or get mishandled during recycling, it causes harm. Health problems associated with such toxins include impaired mental development, cancer, and damage to the lungs, liver, and kidneys. [24] That's why even wires have to be recycled. Different companies have different techniques to recycle a wire. The most popular one is the grinder that separates the copper wires from the plastic/rubber casing. When the processes are done there are two different piles left; one containing the copper powder, and the other containing plastic/rubber pieces. [25] Computer monitors, mice, and keyboards all have a similar way of being recycled. For example, first, each of the parts are taken apart then all of the inner parts get separated and placed into its own bin. [26]

Computer components contain many toxic substances, like dioxins, polychlorinated biphenyls (PCBs), cadmium, chromium, radioactive isotopes and mercury. A typical computer monitor may contain more than 6% lead by weight, much of which is in the lead glass of the cathode ray tube (CRT). A typical 15 inch (38 cm) computer monitor may contain 1.5 pounds (1 kg) of lead [27] but other monitors have been estimated to have up to 8 pounds (4 kg) of lead. [28] Circuit boards contain considerable quantities of lead-tin solders that are more likely to leach into groundwater or create air pollution due to incineration. In US landfills, about 40% of the lead content levels are from e-waste. [29] The processing (e.g. incineration and acid treatments) required to reclaim these precious substances may release, generate, or synthesize toxic byproducts.

Recycling of computer hardware is considered environmentally friendly because it prevents hazardous waste, including heavy metals and carcinogens, from entering the atmosphere, landfill or waterways. While electronics consist a small fraction of total waste generated, they are far more dangerous. There is stringent legislation designed to enforce and encourage the sustainable disposal of appliances, the most notable being the Waste Electrical and Electronic Equipment Directive of the European Union and the United States National Computer Recycling Act. [30]

Efforts for minimizing computer hardware waste

As computer hardware contain a wide number of metals inside, the United States Environmental Protection Agency (EPA) encourages the collection and recycling of computer hardware. "E-cycling", the recycling of computer hardware, refers to the donation, reuse, shredding and general collection of used electronics. Generically, the term refers to the process of collecting, brokering, disassembling, repairing and recycling the components or metals contained in used or discarded electronic equipment, otherwise known as electronic waste (e-waste). "E-cyclable" items include, but are not limited to: televisions, computers, microwave ovens, vacuum cleaners, telephones and cellular phones, stereos, and VCRs and DVDs just about anything that has a cord, light or takes some kind of battery. [31]

Recycling a computer is made easier by a few of the national services, such as Dell and Apple. Both companies will take back the computer of their make or any other make. Otherwise a computer can be donated to Computer Aid International which is an organization that recycles and refurbishes old computers for hospitals, schools, universities, etc. [32]

See also

Related Research Articles

Bus (computing) communication system that transfers data between components inside a computer

In computer architecture, a bus is a communication system that transfers data between components inside a computer, or between computers. This expression covers all related hardware components and software, including communication protocols.

Processor design is the design engineering task of creating a processor, a key component of computer hardware. It is a subfield of computer engineering and electronics engineering (fabrication). The design process involves choosing an instruction set and a certain execution paradigm and results in a microarchitecture, which might be described in e.g. VHDL or Verilog. For microprocessor design, this description is then manufactured employing some of the various semiconductor device fabrication processes, resulting in a die which is bonded onto a chip carrier. This chip carrier is then soldered onto, or inserted into a socket on, a printed circuit board (PCB).

Motherboard main printed circuit board (PCB) for a computing device

A motherboard is the main printed circuit board (PCB) found in general purpose computers and other expandable systems. It holds, and allows, communication between many of the crucial electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard usually contains significant sub-systems such as the central processor, the chipset's input/output and memory controllers, interface connectors, and other components integrated for general purpose use and applications.

System on a chip type of integrated circuit

A system on chip is an integrated circuit that integrates all components of a computer or other electronic system. These components typically include a central processing unit (CPU), memory, input/output ports and secondary storage – all on a single substrate or microchip, the size of a coin. It may contain digital, analog, mixed-signal, and often radio frequency signal processing functions, depending on the application. As they are integrated on a single substrate, SoCs consume much less power and take up much less area than multi-chip designs with equivalent functionality. Because of this, SoCs are very common in the mobile computing and edge computing markets. Systems-on-chip are typically fabricated using metal–oxide–semiconductor (MOS) technology, and are commonly used in embedded systems and the Internet of Things.

A video card is an expansion card which generates a feed of output images to a display device. Frequently, these are advertised as discrete or dedicated graphics cards, emphasizing the distinction between these and integrated graphics. At the core of both is the graphics processing unit (GPU), which is the main part that does the actual computations, but should not be confused with the video card as a whole, although "GPU" is often used to refer to video cards.

Overclocking Action of increasing a components clock rate

In computing, overclocking is the practice of increasing the clock rate of a computer to exceed that certified by the manufacturer. Commonly operating voltage is also increased to maintain a component's operational stability at accelerated speeds. Semiconductor devices operated at higher frequencies and voltages increase power consumption and heat. An overclocked device may be unreliable or fail completely if the additional heat load is not removed or power delivery components cannot meet increased power demands. Many device warranties state that overclocking and/or over-specification voids any warranty.

Laptop Personal computer for mobile use

A laptop, often called a notebook, is a small, portable personal computer (PC) with a "clamshell" form factor, typically having a thin LCD or LED computer screen mounted on the inside of the upper lid of the clamshell and an alphanumeric keyboard on the inside of the lower lid. The clamshell is opened up to use the computer. Laptops are folded shut for transportation, and thus are suitable for mobile use. Its name comes from lap, as it was deemed to be placed on a person's lap when being used. Although originally there was a distinction between laptops and notebooks, as of 2014, there is often no longer any difference. Today, laptops are commonly used in a variety of settings, such as at work, in education, for playing games, Internet surfing, for personal multimedia, and general home computer use.

A quiet PC is a personal computer that makes very little or no noise. Common uses for quiet PCs include video editing, sound mixing and home theater PCs, but noise reduction techniques can also be used to greatly reduce the noise from servers. There is currently no standard definition for a "quiet PC", and the term is generally not used in a business context, but by individuals and the businesses catering to them.

Chipset set of electronic components in an integrated circuit that manages the data flow between the processor, memory and peripherals

In a computer system, a chipset is a set of electronic components in an integrated circuit known as a "Data Flow Management System" that manages the data flow between the processor, memory and peripherals. It is usually found on the motherboard. Chipsets are usually designed to work with a specific family of microprocessors. Because it controls communications between the processor and external devices, the chipset plays a crucial role in determining system performance.

Northbridge (computing) chip on a computer motherboard

A northbridge or host bridge is one of the two chips in the core logic chipset architecture on a PC motherboard, the other being the southbridge. Unlike the southbridge, northbridge is connected directly to the CPU via the front-side bus (FSB) and is thus responsible for tasks that require the highest performance. The northbridge, also known as Memory Controller Hub, is usually paired with a southbridge. In systems where they are included, these two chips manage communications between the CPU and other parts of the motherboard, and constitute the core logic chipset of the PC motherboard.

Video display controller type of integrated circuit

A video display controller or VDC is an integrated circuit which is the main component in a video signal generator, a device responsible for the production of a TV video signal in a computing or game system. Some VDCs also generate an audio signal, but that is not their main function.

Gaming computer personal computer designed for playing video games

A gaming computer, also known as a gaming PC or gaming rig, is a personal computer designed for playing video games that require a high amount of computing power. A modern gaming computer is comparable to a mainstream computer with the addition of performance-oriented components, such as high-performance video cards and high core-count central processing units, that sacrifice power efficiency for raw performance. Gaming computers are often associated with enthusiast computing due to an overlap in interests; however, while a gaming computer is built to achieve performance for actual gameplay, enthusiast PCs are built to maximize performance, using games as a real application benchmark. Whereas enthusiast PCs are high-end by definition, gaming PCs can be subdivided into low-end, mid-range, and high-end markets. Video card manufacturers earn the bulk of their revenue from their low-end and mid-range offerings. Gaming PCs are often also suitable for other intensive tasks, like video editing.

Transistor count the number of transistors in a device

The transistor count is the number of transistors on an integrated circuit (IC). It typically refers to the number of MOSFETs on an IC chip, as all modern ICs use MOSFETs. It is the most common measure of IC complexity. The rate at which MOS transistor counts have increased generally follows Moore's law, which observed that the transistor count doubles approximately every two years.

Enthusiast computing refers to a sub-culture of personal computer users who focus on extremely high-end computers. Manufacturers of performance-oriented parts typically include an enthusiast model in their offerings. Enthusiast computers commonly feature extravagant cases and high-end components, and are sometimes liquid cooled.

A computer is a machine that can be instructed to carry out sequences of arithmetic or logical operations automatically via computer programming. Modern computers have the ability to follow generalized sets of operations, called programs. These programs enable computers to perform an extremely wide range of tasks. A "complete" computer including the hardware, the operating system, and peripheral equipment required and used for "full" operation can be referred to as a computer system. This term may as well be used for a group of computers that are connected and work together, in particular a computer network or computer cluster.

Personal computer Computer intended for use by an individual person

A personal computer (PC) is a multi-purpose computer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or technician. Unlike large costly minicomputers and mainframes, time-sharing by many people at the same time is not used with personal computers.

Random-access memory Form of computer data storage

Random-access memory is a form of computer memory that can be read and changed in any order, typically used to store working data and machine code. A random-access memory device allows data items to be read or written in almost the same amount of time irrespective of the physical location of data inside the memory. In contrast, with other direct-access data storage media such as hard disks, CD-RWs, DVD-RWs and the older magnetic tapes and drum memory, the time required to read and write data items varies significantly depending on their physical locations on the recording medium, due to mechanical limitations such as media rotation speeds and arm movement.

GPU switching

GPU switching is a mechanism used on computers with multiple graphic controllers. This mechanism allows the user to either maximize the graphic performance or prolong battery life by switching between the graphic cards. It's mostly used on gaming laptops which usually have an integrated graphic device and a discrete video card.

This glossary of computer hardware terms is a list of definitions of terms and concepts related to computer hardware, i.e. the physical and structural components of computers, architectural issues, and peripheral devices.

Computers can be classified, or typed, in many ways. Some common classifications of digital computers are summarized below. For others see Category:Classes of computers.

References

  1. 1 2 PC hardware : a beginner's guide. Osborne/McGraw-Hill. p. 21. ISBN   9780072129908.
  2. "Parts of computer". Microsoft. Archived from the original on 27 November 2013. Retrieved 5 December 2013.
  3. von Neumann, John (1945). "First Draft of a Report on the EDVAC" (PDF). Archived from the original (PDF) on 9 August 2013. Retrieved 6 December 2013.Cite journal requires |journal= (help)
  4. Markgraf, Joey D. (2007). "The Von Neumann bottleneck". Archived from the original on 9 June 2011. Retrieved 24 August 2011.
  5. "Desktop computer vs. Laptop computer". www.computerhope.com. 30 December 2019. Retrieved 15 January 2020.
  6. "How long should a laptop battery last?". Computer Hope. Archived from the original on 21 December 2013. Retrieved 9 December 2013.
  7. 1 2 Harding, Scharon (17 September 2019). "What Is a MOSFET? A Basic Definition". Tom's Hardware . Retrieved 7 November 2019.
  8. "13 Sextillion & Counting: The Long & Winding Road to the Most Frequently Manufactured Human Artifact in History". Computer History Museum . 2 April 2018. Retrieved 28 July 2019.
  9. Domingo, Joel. "SSD vs. HDD: What's the Difference?". PCMag. Archived from the original on 19 March 2017. Retrieved 24 March 2017.
  10. Edwards, Benj (17 January 2012). "Evolution of the Solid-State Drive". PCWorld. Archived from the original on 25 March 2017. Retrieved 24 March 2017.
  11. PC hardware : a beginner's guide. Osborne/McGraw-Hill. 2001. p. 20. ISBN   9780072129908.
  12. Henderson, Rebecca M.; Newell, Richard G., eds. (2011). Accelerating energy innovation : insights from multiple sectors. Chicago: University of Chicago Press. p. 180. ISBN   978-0226326832.
  13. Huang, Han-Way (2014). The atme AVR microcontroller : MEGA and XMEGA in assembly and C. Australia ; United Kingdom: Delmar Cengage Learning. p. 4. ISBN   978-1133607298.
  14. Estabrooks, Maurice (1995). Electronic technology, corporate strategy, and world transformation . Westport, Conn.: Quorum Books. p.  53. ISBN   0899309690.
  15. "Global revenue from computer hardware from 2005 to 2016". Statista. Retrieved 15 January 2020.
  16. "How to recycle your old computer". Digital Trends. 18 December 2016. Archived from the original on 17 April 2017. Retrieved 18 April 2017.
  17. Inc, Chris Keenan - Newtech Recycling. "Newtech Recycling Specializes in Computer Disposal, Laptop Disposal, Desktop Disposal Mainframe Disposal and Server Disposal". www.newtechrecycling.com. Archived from the original on 29 March 2017. Retrieved 18 April 2017.
  18. Robert-Tissot, Sarah (2011). "TANTALUM". Royal Australian Chemical instatute. Retrieved 3 March 2019.
  19. Padilla, Abraham (February 2019). "TANTALUM" (PDF). United states geological survey. Retrieved 3 March 2019.
  20. Bleiwas, D (July 2001). "Obsolete Computers, "Gold Mine," or High-Tech Trash? Resource Recovery from Recycling" (PDF). USGS. Retrieved 4 March 2019.
  21. Lubell, Ilene. "Did you know your computer contains precious metals?". info.mayermetals.com. Retrieved 4 March 2019.
  22. LeBlanc, Rick. "Electronic Devices a Rich Source of Precious Metals for Recyclers". The Balance Small Business. Retrieved 4 March 2019.
  23. "The Toxic Components of Computers and Monitors". Archived from the original on 27 April 2017. Retrieved 26 April 2017.
  24. "What's Going On with Electronic Waste? – Electronics TakeBack Coalition". Archived from the original on 27 April 2017. Retrieved 26 April 2017.
  25. "Wire Recycling". All-Recycling-Facts.com. Archived from the original on 10 July 2017. Retrieved 5 May 2017.
  26. "Computer equipment recycling – Essential Guide". ComputerWeekly. Archived from the original on 21 December 2016. Retrieved 8 May 2017.
  27. Morgan, Russell (21 August 2006). "Tips and Tricks for Recycling Old Computers". SmartBiz. Retrieved 17 March 2009.
  28. Royte, Elizabeth (1 August 2005). "E-gad! Americans discard more than 100 million computers, cellphones and other electronic devices each year. As "e-waste" piles up, so does concern about this growing threat to the environment". Smithsonian Magazine . Smithsonian Institution . Retrieved 17 March 2009.
  29. Toothman, Jessika. "What Happens to your Discarded Old Computer?". HowStuffWorks.
  30. National Computer Recycling Act of 2005, H.R. 425, 109th Cong. (2005–2006)
  31. T. Gallo, Daniel (15 July 2013). "Broad Overview of E-Waste Management Policies in the U.S." (PDF). www.epa.gov. Retrieved 17 January 2020.
  32. Schofield, Jack (19 February 2015). "How can I safely recycle my old PCs?". The Guardian. ISSN   0261-3077. Archived from the original on 27 April 2017. Retrieved 26 April 2017.