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===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}}
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 GHz andto 5 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>
Because computer parts contain [[hazard]]ous materials, there is a growing movement to recycle old and outdated devices.<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 contains hazardous substances such as lead, mercury, nickel, and cadmium. According to the [[United States Environmental Protection Agency|EPA]], these e-wastes negatively affect the [[Natural environment|environment]] if not disposed of properly. Hardware manufacturing also requires significant energy, while [[recycling]] components helps reduce air and 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> In many regions, improper disposal of computer equipment is illegal, and legislation requires recycling through [[government]]-approved facilities. Recycling can be facilitated by removing reusable parts such as [[Random-access memory|RAM]], DVD drives, [[Graphics hardware|graphics cards]], [[Hard disk drive|hard drives]], [[Solid-state drive|SSDs]], and other similar components.
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===
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