Computer hardware: Difference between revisions

Revision as of 09:55, 19 August 2025

Revision as of 11:49, 19 August 2025

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* At least one [[central processing unit|CPU]] (central processing unit), which performs the majority of computational tasks required for a computer to operate.{{sfn|Wang|2021|p=8}} Often described informally as the "brain" of the computer,{{sfn|Wang|2021|p=9}} the CPU fetches program instructions from [[random-access memory]] (RAM), decodes and executes them, then returns results for further processing by other components. This process is known as the [[instruction cycle]]. Modern CPUs are [[microprocessor]]s fabricated on a [[metal–oxide–semiconductor]] (MOS) [[integrated circuit]] (IC) using advanced [[semiconductor device fabrication]] techniques, often employing [[photolithography]]. They are typically cooled using a [[heatsink]] and [[computer fan|fan]] or a [[liquid cooling|liquid-cooling system]]. Many contemporary CPUs integrate an on-die [[graphics processing unit]] ([[integrated graphics|GPU]]), eliminating the need for a discrete GPU in basic systems. CPU performance is influenced by clock speed—measured in gigahertz (GHz)—with common consumer processors ranging from 1 GHz to 5 GHz.{{cn|date=August 2024}} Additionally, there is a growing trend toward [[multi-core processor|multi-core designs]], where multiple processing cores are included on a single chip, enabling greater [[parallel computing|parallelism]] and improved multitasking performance.{{sfn|Wang|2021|p=9}}

*The internal bus connects the CPU to main memory via multiple communication lines—typically 50 to 100—divided into address, data, and control buses, each handling specific types of signals.{{sfn|Wang|2021|p=75}} Historically, parallel buses were dominant, but in the twenty-first century, high-speed serial buses (often using [[serializer/deserializer]] (SerDes) technology) have largely replaced them, enabling greater data throughput over fewer physical connections. Examples include [[PCI Express]] and [[USB]].{{sfn|Wang|2021|p=78}} In systems with multiple processors, an interconnect bus is used, traditionally coordinated by a [[Northbridge (computing)|northbridge]] chip, which links the CPU, memory, and high-speed peripherals such as [[PCI]]. The [[Southbridge (computing)|southbridge]] handles communication with slower 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), which stores the [[BIOS]] that runs when the computer is powered on or otherwise begins execution, a process known as [[Bootstrapping (computing)|Bootstrapping]], or [[booting]] or booting up.{{cn|date=August 2024}} The ROM is typically a [[nonvolatile BIOS memory]] chip, which can only be written once with special technology.{{sfn|Wang|2021|p=55}}