Computer hardware: Difference between revisions

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[[File:PDP-11-M7270.jpg|thumb|upright|[[PDP-11]] CPU board]]

'''Computer hardware''' includes the physical parts of a [[computer]], such as the [[central processing unit]] (CPU), [[Randomrandom-access memory|random access memory]] (RAM)]], [[motherboard]], [[computer data storage]], [[graphics card]], [[sound card]], and [[computer case]]. It includes external devices such as a [[Computer monitor|monitor]], [[Computer mouse|mouse]], [[Computer keyboard|keyboard]], and [[Computer speakers|speakers]].<ref>{{cite web |title=Parts of computer |url=http://windows.microsoft.com/en-us/windows-vista/parts-of-a-computer |publisher=Microsoft |access-date=5 December 2013 |url-status=live |archive-url=https://web.archive.org/web/20131127145607/http://windows.microsoft.com/en-US/windows-vista/Parts-of-a-computer |archive-date=27 November 2013 |df=dmy-all }}</ref><ref>{{Cite book |last=Gilster |first=Ron |url=http://archive.org/details/pchardwarebeginn00gils |title=PC hardware : a beginner's guide |date=2001 |publisher=New York; London : McGraw-Hill |others=Internet Archive |isbn=978-0-07-212990-8}}</ref>

By contrast, [[software]] is a set of written instructions that can be stored and run by hardware. Hardware derived its name from the fact it is ''[[Hardness|hard]]'' or rigid with respect to changes, whereas software is ''soft'' because it is easy to change.

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Early computing devices were more complicated than the ancient [[abacus]] date to the seventeenth century. French mathematician [[Blaise Pascal]] designed a gear-based device that could add and subtract, selling around 50 models. The [[stepped reckoner]] was invented by [[Gottfried Leibniz]] by 1676, which could also divide and multiply. Due to the limitations of contemporary fabrication and design flaws, Leibniz' reckoner was not very functional, but similar devices ([[Leibniz wheel]]) remained in use into the 1970s.{{sfn|Blum|2011|p=13–14}} In the 19th century, Englishman [[Charles Babbage]] invented the [[difference engine]], a mechanical device to calculate [[polynomial]]s for astronomical purposes.{{sfn|Blum|2011|p=14}} Babbage also designed a general-purpose computer that was never built. Much of the design was incorporated into the earliest computers: [[punch card]]s for input and output, [[memory (computing)|memory]], an arithmetic unit analogous to [[central processing unit]]s, and even a primitive [[programming language]] similar to [[assembly language]].{{sfn|Blum|2011|p=15}}

In 1936, [[Alan Turing]] developed the concept of the [[universal Turing machine]] to model any type of computer, provingdemonstrating that no computermachine would be able tocould solve the [[Entscheidungsproblem|decision problem]].
{{sfn|Blum|2011|pp=21, 23}} The universal Turing machine was a type of [[stored-program computer]] capable of mimicking the operations of any [[Turing machine]] (computer model) based on the [[software]] instructions passed to it. The storage of [[computer program]]s is key to the operation of modern computers and is the connection between computer hardware and software.{{sfn|Blum|2011|p=25}} Even prior to this, in the mid-19th century mathematician [[George Boole]] invented [[Boolean algebra]]—a system of logic where each [[proposition]] is either true or false. Boolean algebra is now the basis of the [[circuit (computer science)|circuit]]s that model the [[transistor]]s and other components of [[integrated circuit]]s that make up modern computer hardware.{{sfn|Blum|2011|pp=34-35}} In 1945, Turing finished the design for a computer (the [[Automatic Computing Engine]]) that was never built.{{sfn|Blum|2011|pp=71-72}}

[[File:Von Neumann Architecture.svg|thumb|Von Neumann architecture scheme]]

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[[File:Growth in processor performance, 1978–2010.png|thumb|Growth in processor performance (as measured by benchmarks),{{sfn|Hennessy |Patterson|2011|pp=41-42}} 1978–2010]]

Computer architecture requiresinvolves prioritizingbalancing between differentvarious goals, such as cost, speed, availability, and energy efficiency. The designerDesigners must have a goodthorough graspunderstanding of the hardware requirements and many differentdiverse aspects of computing, ranging from [[compiler]]s to integrated[[Integrated circuit design]]. {{sfn|Hennessy |Patterson|2011|p=11}} Cost has also become a significant constraint for manufacturers seeking to sell their products for less money than competitors offering a very similar hardware component. Profit margins have also been reduced.{{sfn|Hennessy |Patterson|2011|pp=27-28, 32}} Even when the performance is not increasing, the cost of components has been dropping over time due to improved manufacturing techniques that have fewer components rejected at [[quality assurance]] stage.{{sfn|Hennessy |Patterson|2011|p=27}}

===Instruction set architecture===

The most common [[instruction set architecture]] (ISA)—the interface between a computer's hardware and software—is based on the one devised by von Neumann in 1945.{{sfn|Mendelson|2022|p=2}} Despite the separation of the computing unit and the I/O system in many diagrams, typically the hardware is shared, with a bit in the computing unit indicating whether it is in computation or I/O mode.{{sfn|Mendelson|2022|pp=2-3}} Common types of ISAs include CISC ([[complex instruction set computer]]), RISC ([[reduced instruction set computer]]), [[Vector processor|vector operations]], and hybrid modes.{{sfn|Mendelson|2022|p=3}} CISC involves using a larger expression set to minimize the number of instructions the machines need to use.{{sfn|Mendelson|2022|p=8}} Based on a recognition that only a few instructions are commonly used, RISC shrinks the instruction set for added simplicity, which also enables the inclusion of more [[register (computing)|register]]s.{{sfn|Mendelson|2022|p=15}} After the invention of RISC in the 1980s, RISC based architectures that used [[Pipeline (computing)|pipelining]] and [[caching]] to increase performance displaced CISC architectures, particularly in applications with restrictions on power usage or space (such as [[mobile phone]]s). From 1986 to 2003, the annual rate of improvement in hardware performance exceeded 50 percent, enabling the development of new computing devices such as [[Tablet computer|tablet]]s and mobiles.{{sfn|Hennessy |Patterson|2011|p=2}} Alongside the density of transistors, DRAM memory as well as flash and magnetic disk storage also became exponentially more compact and cheaper. The rate of improvement slackened off in the twenty-first century.{{sfn|Hennessy |Patterson|2011|pp=17–18}}

In the twenty-first century, increases in performance have been driven by increasing exploitation of [[Parallel computing|parallelism]].{{sfn|Hennessy |Patterson|2011|pp=9, 44}} Applications are often parallelizable in two ways: either the same function is running across multiple areas of data ([[data parallelism]]) or different tasks can be performed simultaneously with limited interaction ([[task parallelism]]).{{sfn|Hennessy |Patterson|2011|p=9}} These forms of parallelism are accommodated by various hardware strategies, including [[instruction-level parallelism]] (such as [[instruction pipelining]]), vector architectures and [[graphical processing unit]]s (GPUs) that are able to implement data parallelism, thread-level parallelism and request-level parallelism (both implementing task-level parallelism).{{sfn|Hennessy |Patterson|2011|p=9}}

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[[Microarchitecture]], also known as computer organization, refers to high-level hardware questions such as the design of the CPU, memory, and memory [[interconnect (integrated circuits)|interconnect]].{{sfn|Hennessy |Patterson|2011|p=15}} [[Memory hierarchy]] ensures that the memory quicker to access (and more expensive) is located closer to the CPU, while slower, cheaper memory for large-volume storage is located further away.{{sfn|Wang|2021|p=3}} Memory is typically segregated to separate programs from data and limit an attacker's ability to alter programs.{{sfn|Wang|2021|p=4}} Most computers use [[virtual memory]] to simplify addressing for programs, using the [[operating system]] to map virtual memory to different areas of the finite physical memory.{{sfn|Wang|2021|pp=51-52}}

===ASUTOSHCooling===

Computer processors generate heat, and excessive heat impacts their performance and can harm the components. Many computer chips will automatically throttle their performance to avoid overheating. Computers also typically have mechanisms for dissipating excessive heat, such as air or liquid coolers for the CPU and GPU and heatsinks for other components, such as the [[RAM]]. [[Computer case]]s are also often ventilated to help dissipate heat from the computer.<ref>{{cite web |title=PC Cooling: The Importance of Keeping Your PC Cool |url=https://www.intel.com/content/www/us/en/gaming/resources/pc-cooling-the-importance-of-keeping-your-pc-cool.html |website=Intel |access-date=20 July 2024 |language=en}}</ref> [[Data center]]s typically use more sophisticated cooling solutions to keep the operating temperature of the entire center safe. Air-cooled systems are more common in smaller or older data centers, while liquid-cooled immersion (where each computer is surrounded by cooling fluid) and direct-to-chip (where the cooling fluid is directed to each computer chip) can be more expensive but are also more efficient.<ref>{{cite web |title=Data Center Cooling: What are the top concepts you need to know? |url=https://gatewaymechanical.ca/data-center-cooling-what-you-need-to-know/ |website=gatewaymechanical.ca |access-date=20 July 2024 |language=en-CA |date=11 August 2021}}</ref> Most computers are designed to be more powerful than their cooling system, but their sustained operations cannot exceed the capacity of the cooling system.{{sfn|Hennessy |Patterson|2011|p=22}} While performance can be temporarily increased when the computer is not hot ([[overclocking]]),{{sfn|Hennessy |Patterson|2011|p=26}} in order to protect the hardware from excessive heat, the system will automatically reduce performance or shut down the processor if necessary.{{sfn|Hennessy |Patterson|2011|p=22}} Processors also will shut off or enter a low power mode when inactive to reduce heat.{{sfn|Hennessy |Patterson|2011|p=25}} Power delivery as well as heat dissipation are the most challenging aspects of hardware design,{{sfn|Hennessy |Patterson|2011|p=21}} and have been the limiting factor to the development of smaller and faster chips since the early twenty-first century.{{sfn|Hennessy |Patterson|2011|p=25}} Increases in performance require a commensurate increase in energy use and cooling demand.{{sfn|Hennessy |Patterson|2011|p=56}}

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[[File:Front Z9 2094.jpg|thumb|upright|An [[IBM System z9]] mainframe]]

*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.

*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 [[computer]]s that was developed in the mid-1960s<ref>{{cite book|editor-last1=Henderson|editor-first1=Rebecca M.|editor-last2=Newell|editor-first2=Richard G.|title=Accelerating energy innovation : insights from multiple sectors|date=2011|publisher=University of Chicago Press|___location=Chicago|isbn=978-0226326832|page=180}}</ref><ref>{{cite book |last1=Huang |first1=Han-Way |title=The atmeAtmel AVR microcontroller : MEGA and XMEGA in assembly and C |date=2014 |publisher=Delmar Cengage Learning |isbn=978-1133607298 |___location=Australia; United Kingdom|isbn=978-1133607298 |page=4}}</ref> and sold for much less than [[Mainframe computer|mainframe]]<ref>{{cite book|last1=Estabrooks|first1=Maurice|title=Electronic technology, corporate strategy, and world transformation |url=https://archive.org/details/electronictechno0000esta |url-access=registration|date=1995|publisher=Quorum Books|___location=Westport, Conn.|isbn=0899309690|page=[https://archive.org/details/electronictechno0000esta/page/53 53]}}</ref> and mid-size computers from [[IBM]] and its direct competitors.

*[[Supercomputer]]s can cost hundreds of millions of dollars. They are intendeddesigned to maximize performance within [[floating-point arithmetic]] and runningexecute [[batch processing|batch programs]] that may take a very long time (such as weeks) to complete. AsDue a result ofto the need for efficient communication between [[parallel computing|parallel programs]], the speed of the internal network mustis a becritical prioritizedpriority.{{sfn|Hennessy |Patterson|2011|p=8}}

*[[Warehouse scale computer]]s are larger versions of [[cluster computer]]s that came into fashion with [[software as a service]] provided via [[the internet]]. Their design is intended to minimize cost per operation and power usage, as they can cost over $100 million for a warehouse and the computers which go inside (the computers must be replaced every few years). Although availability is crucial for SaaS products, the software is designed to compensate for availability failures—unlike supercomputers.{{sfn|Hennessy |Patterson|2011|p=8}}

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

* At least one [[central processing unit|CPU]] (central processing unit), which performs mostthe majority of thecomputational calculationstasks thatrequired enablefor a computer to functionoperate.{{sfn|Wang|2021|p=8}} ItOften can bedescribed informally referred to as the ''brain'' of the computer.,{{sfn|Wang|2021|p=9}} Itthe CPU takesfetches program instructions from [[random-access memory]] (RAM), interpretsdecodes and processesexecutes them and, then sends backreturns results sofor thatfurther theprocessing relevantby other components. canThis carryprocess outis theknown instructions.as The CPU is athe [[microprocessorinstruction cycle]],. whichModern isCPUs are [[semiconductor device fabrication|fabricatedmicroprocessor]]s fabricated on a [[metal–oxide–semiconductor]] (MOS) [[integrated circuit]] (IC) chip.using Itadvanced is[[semiconductor device fabrication]] techniques, often usuallyemploying [[CPU cooling|cooledphotolithography]]. byThey are typically cooled using a [[heatsink]] and [[computer fan,|fan]] or watera [[liquid cooling|liquid-cooling system]]. Many newercontemporary CPUs includeintegrate an on-die [[graphics processing unit]] (GPU). The [[clockintegrated speedgraphics|GPU]]), ofeliminating the CPUneed governsfor howa fastdiscrete itGPU executesin instructionsbasic andsystems. CPU performance is measuredinfluenced by clock speed—measured in gigahertz (GHz;)—with typicalcommon valuesconsumer lieprocessors betweenranging from 1&nbsp;GHz andto 5&nbsp;GHz.{{cn|date=August 2024}} ThereAdditionally, there is alsoa an increasinggrowing trend totoward add[[multi-core moreprocessor|multi-core coresdesigns]], towhere amultiple processor—withprocessing eachcores actingare asincluded ifon ita weresingle anchip, independentenabling processor—forgreater increased[[parallel computing|parallelism]] and improved multitasking performance.{{sfn|Wang|2021|p=9}}

*The internal bus connects the CPU to the main memory withvia severalmultiple linescommunication for simultaneous communication—typicallylines—typically 50 to 100—which are separated100—divided into thoseaddress, fordata, addressingand orcontrol memorybuses, data,each andhandling commandspecific ortypes controlof signals.{{sfn|Wang|2021|p=75}} AlthoughHistorically, parallel buses usedwere todominant, bebut morein commonthe twenty-first century, high-speed serial buses with(often ausing [[serializer/deserializer]] to(SerDes) sendtechnology) morehave informationlargely overreplaced thethem, sameenabling wiregreater havedata becomethroughput moreover commonfewer inphysical theconnections. twenty-firstExamples centuryinclude [[PCI Express]] and [[USB]].{{sfn|Wang|2021|p=78}} ComputersIn systems with multiple processors will need, an interconnectioninterconnect bus is used, usuallytraditionally managedcoordinated by a [[Northbridge (computing)|northbridge]] chip, whilewhich links the CPU, memory, and high-speed peripherals such as [[PCI]]. The [[Southbridge (computing)|southbridge]] manageshandles communication with slower peripheral and I/O devices such as storage and USB ports.{{sfn|Wang|2021|p=90}} However, in modern architectures like [[Intel QuickPath Interconnect]] or [[AMD Ryzen]]-based systems, these functions are increasingly integrated into the CPU itself, forming a [[system on a chip]] (SoC)-like design.

*[[Random-access memory]] (RAM), which stores the code and data that are being actively accessedused by the CPU, organized in a [[memory hierarchy]] basedoptimized onfor whenaccess itspeed isand expectedpredicted toreuse. beAt nextthe used.top of this hierarchy are [[Processorprocessor register|Registerregisters]]s, are closestlocated towithin the CPU butcore, haveoffering verythe fastest access but extremely limited capacity.{{sfn|Wang|2021|p=47}} CPUsBelow alsoregisters typically haveare multiple areaslevels of [[cache memory]]—L1, thatL2, haveand muchsometimes moreL3—typically implemented using [[static random-access memory]] (SRAM). Caches have greater capacity than registers, but much less than main memory;, theyand arewhile slower to access than registers, butthey muchare significantly faster than main[[dynamic random-access memory]] (DRAM), which is used for main RAM.{{sfn|Wang|2021|pp=49-5049–50}} Caching worksimproves performance by [[prefetching]] datafrequently beforeused thedata, CPUthereby needsreducing it, reducing[[memory latency]].{{sfn|Wang|2021|pp=49-5049–50}}{{sfn|Hennessy |Patterson|2011|p=45}} If theWhen data the CPU needs is not found in the cache (a [[cache miss]]), it canis be accessedretrieved from main memory.{{sfn|Wang|2021|pp=49-50}} [[Cache memory]]RAM is typicallyvolatile, [[Staticmeaning random-accessits memory|SRAM]],contents whileare thelost mainwhen memorythe issystem typicallyloses [[DRAM]]power.{{sfn|Wang|2021|p=354}} RAMIn ismodern volatilesystems, meaningDRAM itsis contentsoften willof disappearthe if[[DDR theSDRAM]] computertype, such powersas downDDR4 or DDR5.{{sfn|Wang|2021|p=54}}

*Permanent storage or non-volatile memory is typically higher capacity and cheaper than memory, but takes much longer to access. Historically, such storage was typically provided in the form of a hard drive, but [[solid-state drives]] (SSD) are becoming cheaper and are much faster, thus leading to their increasing adoption. USB drives and network or cloud storage are also options.{{sfn|Wang|2021|pp=55–56}}

*[[Read-only memory]] (ROM), whichcontains storesfirmware such as the [[BIOS]] that(Basic runsInput/Output whenSystem), thewhich computerinitializes ishardware poweredduring onthe orboot otherwiseprocess—known beginsas execution,[[booting]] a process known asor [[Bootstrappingbootstrapping (computing)|Bootstrappingbootstrapping]],—when orthe [[booting]]computer oris bootingpowered upon.{{cn|date=August 2024}} TheThis ROMfirmware is typicallystored in a non-volatile memory chip, traditionally ROM or [[nonvolatile BIOSflash memory]] chip, whichallowing canupdates onlyin bemodern writtensystems oncevia with[[firmware special technologyupdate]].{{sfn|Wang|2021|p=55}}

** The [[BIOS]] (Basicmanages Inputessential Outputfunctions System) includesincluding boot [[firmware]]sequence and power management firmwarethrough the [[ACPI]] standard. NewerHowever, most modern motherboards usehave transitioned to the [[Unified Extensible Firmware Interface]] (UEFI), insteadwhich ofoffers BIOSenhanced capabilities, faster startup times, support for [[GUID Partition Table]] (GPT), and secure boot features.

* The [[CMOS]] (complementary MOS) [[electric battery|battery]], which powers the [[CMOS memory]] for date and time in the BIOS chip. This battery is generally a [[watch battery]].

*[[Power MOSFET]]s make up the [[voltage regulator module]] (VRM), which controls how much [[voltage]] other hardware components receive.<ref name="tomshardware">{{cite web |last1=Harding |first1=Scharon |title=What Is a MOSFET? A Basic Definition |url=https://www.tomshardware.com/uk/reviews/mosfet-defintion-transistor-pc-motherboard-psu-explained,6343.html |website=[[Tom's Hardware]] |access-date=7 November 2019 |date=September 17, 2019}}</ref>

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{{main|Computer recycling}}

Because computer parts contain [[hazard]]ous materials, there is a growing movement to recycle old and outdated partsdevices.<ref>{{Cite news|url=http://www.digitaltrends.com/computing/how-to-recycle-your-old-computer/|title=How to recycle your old computer|date=2016-12-18|work=Digital Trends|access-date=2017-04-18|language=en-US|url-status=live|archive-url=https://web.archive.org/web/20170417055533/http://www.digitaltrends.com/computing/how-to-recycle-your-old-computer/|archive-date=17 April 2017|df=dmy-all}}</ref> Computer hardware containcontains dangeroushazardous chemicalssubstances such as lead, mercury, nickel, and cadmium. According to the [[United States Environmental Protection Agency|EPA]], these e-wastes havenegatively a harmful effect onaffect the [[Natural environment|environment]] unlessif they arenot disposed of properly. MakingHardware hardwaremanufacturing also requires significant energy, andwhile [[recycling]] partscomponents willhelps reduce air and water [[pollution]], water pollution, as well as greenhouse gas emissions.<ref>{{Cite web|url=https://www.newtechrecycling.com/disposal/computer-recycling/computer-recycling.html|title=Newtech Recycling Specializes in Computer Disposal, Laptop Disposal, Desktop Disposal Mainframe Disposal and Server Disposal|website=Newtech Recycling, Inc.|archive-url=https://web.archive.org/web/20170329142805/https://www.newtechrecycling.com/disposal/computer-recycling/computer-recycling.html|archive-date=29 March 2017|url-status=dead|access-date=2017-04-18|df=dmy-all}}</ref> DisposingIn unauthorizedmany regions, improper disposal of computer equipment is in fact illegal., Legislationand makeslegislation itrequires mandatory to [[Recycling|recycle]] computersrecycling through the [[government]] -approved facilities. Recycling a computer can be made easierfacilitated by taking out certainremoving reusable parts. Forsuch example, theas [[Random-access memory|RAM]], DVD drivedrives, the [[Graphics hardware|graphics cardcards]], [[Hard disk drive|hard drivedrives]] or, [[Solid-state drive|SSDSSDs]], and other similar removable parts can be reusedcomponents.

Many materials used in computer hardware can be recovered bythrough recycling for use in future production. ReuseThe reuse of [[tin]], [[silicon]], [[iron]], [[aluminum]], and a variety ofvarious [[plastics]] thatcommonly are present in bulkfound in computers orand other electronics canhelps reduce the costs of constructingmanufacturing new systems. ComponentsHardware components also frequently contain [[copper]], [[gold]], [[tantalum]],<ref>{{Cite web|url=https://www.raci.org.au/document/item/488|title=TANTALUM|last=Robert-Tissot|first=Sarah|date=2011|website=Royal Australian Chemical instatuteInstitute|access-date=March 3, 2019|archive-date=26 February 2017|archive-url=https://web.archive.org/web/20170226021016/https://www.raci.org.au/document/item/488|url-status=dead}}</ref><ref>{{Cite web|url=https://minerals.usgs.gov/minerals/pubs/commodity/niobium/mcs-2019-tanta.pdf|title=TANTALUM|last=Padilla|first=Abraham|date=February 2019|website=United statesStates geologicalGeological surveySurvey|access-date=March 3, 2019}}</ref> [[silver]], [[platinum]], [[palladium]], and [[lead]], as wellalong aswith other valuable materials suitable for reclamation.<ref>{{Cite web|url=https://pubs.usgs.gov/fs/fs060-01/fs060-01.pdf|title=Obsolete Computers, "Gold Mine," or High-Tech Trash? Resource Recovery from Recycling|last=Bleiwas|first=D|date=July 2001|website=USGS|access-date=March 4, 2019}}</ref><ref>{{Cite web|url=https://www.thebalancesmb.com/electronic-devices-source-of-metals-for-recyclers-2877986|title=Electronic Devices a Rich Source of Precious Metals for Recyclers|last=LeBlanc|first=Rick|website=The Balance Small Business|language=en|access-date=2019-03-04}}</ref>

===Toxic computer components===

The [[central processing unit]] contains manyseveral toxic materials. It containsmay include lead and chromium in the metal plates. Resistors, semiconductors, infrared detectors, stabilizers, cables, and wires can contain cadmium., Thewhile computer circuit boards inmay a computeralso contain mercury, and chromium.<ref>{{Cite news|url=http://smallbusiness.chron.com/toxic-components-computers-monitors-69693.html|title=The Toxic Components of Computers and Monitors|access-date=2017-04-26|language=en|url-status=live|archive-url=https://web.archive.org/web/20170427192255/http://smallbusiness.chron.com/toxic-components-computers-monitors-69693.html|archive-date=27 April 2017|df=dmy-all}}</ref> WhenImproper these typesdisposal of these materials, and chemicals are disposed improperlycan willpose becomeserious hazardoushazards forto the environment.

===Environmental effects===

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.<ref>{{Cite web|url=http://www.electronicstakeback.com/2015/05/28/whats-going-on-with-electronic-waste/|title=What's Going On with Electronic Waste? – Electronics TakeBack Coalition|access-date=2017-04-26|url-status=liveusurped|archive-url=https://web.archive.org/web/20170427103038/http://www.electronicstakeback.com/2015/05/28/whats-going-on-with-electronic-waste/|archive-date=27 April 2017|df=dmy-all}}</ref> Computer components contain many toxic substances, like [[Polychlorinated dibenzodioxins|dioxins]], [[polychlorinated biphenyl]]s (PCBs), [[cadmium]], [[chromium]], [[radionuclide|radioactive isotopes]] and [[mercury (element)|mercury]]. Circuit boards contain considerable quantities of lead-tin solders that are more likely to leach into groundwater or create [[air pollution]] due to incineration.<ref name=":0">{{Cite web|url=https://computer.howstuffworks.com/discarded-old-computer1.htm|title=What Happens to your Discarded Old Computer?|last=Toothman|first=Jessika|website=HowStuffWorks|date=2 June 2008}}</ref>

Recycling of computer hardware is considered environmentally friendly because it prevents [[hazardous waste]], including [[Toxic heavy metal|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.<ref>National Computer Recycling Act of 2005, H.R. 425, 109th Cong. (2005–2006)</ref>

===Efforts for minimizing computer hardware waste===

[[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.<ref name="epa-ewaste-presentation">{{Cite web |url=https://www.epa.gov/sites/productiondefault/files/2014-05/documents/overview.pdf |title=Broad Overview of E-Waste Management Policies in the U.S. |last= T. Gallo |first=Daniel |date=2013-07-15 |website=www.epa.gov |access-date=2020-01-17}}</ref>

Some companies, such as [[Dell]] and [[Apple Inc.|Apple]], will recycle computers 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.<ref>{{Cite news|url=https://www.theguardian.com/technology/askjack/2015/feb/19/how-safely-recycle-old-pcs-computers|title=How can I safely recycle my old PCs?|last=Schofield|first=Jack|date=2015-02-19|work=The Guardian|access-date=2017-04-26|language=en-GB|issn=0261-3077|url-status=live|archive-url=https://web.archive.org/web/20170427103349/https://www.theguardian.com/technology/askjack/2015/feb/19/how-safely-recycle-old-pcs-computers|archive-date=27 April 2017|df=dmy-all}}</ref>

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==Sources==

*{{cite book |last1=Blum |first1=Edward K. |title=Computer Science: The Hardware, Software and Heart of It |date=2011 |publisher=Springer Science & Business Media |isbn=978-1-4614-1168-0 |language=en}}

*{{cite book |last1=Hennessy |first1=John L. |last2=Patterson |first2=David A. |title=Computer Architecture: A Quantitative Approach |date=2011 |publisher=Elsevier |isbn=978-0-12-383873383872-58 |language=en}}

*{{cite book |last1=Mendelson |first1=Avi |title=Handbook of Computer Architecture |date=2022 |editor=Anupam Chattopadhyay |publisher=Springer Nature |isbn=978-981-15-6401-7 |pages=1–42 |chapter-url=https://link.springer.com/referenceworkentry/10.1007/978-981-15-6401-7_1-1 |language=en |chapter=The Architecture|doi=10.1007/978-981-15-6401-7_1-1 }}

* {{cite book |last1=Wang |first1=Shuangbao Paul |title=Computer Architecture and Organization: Fundamentals and Architecture Security |date=2021 |publisher=Springer Nature |isbn=978-981-16-5662-0 |language=en}}