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109-553: Microsoft XCPU , codenamed Xenon , is a CPU used in the Xbox 360 game console, to be used with ATI's Xenos graphics chip. The processor was developed by Microsoft and IBM under the IBM chip program codenamed "Waternoose", which was named after the Monsters, Inc. character Henry J. Waternoose III . The development program was originally announced on November 3, 2003. The processor

218-404: A big.LITTLE core includes a high-performance core (called 'big') and a low-power core (called 'LITTLE'). There is also a trend towards improving energy-efficiency by focusing on performance-per-watt with advanced fine-grain or ultra fine-grain power management and dynamic voltage and frequency scaling (i.e. laptop computers and portable media players ). Chips designed from the outset for

327-462: A CPU include the arithmetic–logic unit (ALU) that performs arithmetic and logic operations , processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that orchestrates the fetching (from memory) , decoding and execution (of instructions) by directing the coordinated operations of the ALU, registers, and other components. Modern CPUs devote

436-486: A CPU may also contain memory , peripheral interfaces, and other components of a computer; such integrated devices are variously called microcontrollers or systems on a chip (SoC). Early computers such as the ENIAC had to be physically rewired to perform different tasks, which caused these machines to be called "fixed-program computers". The "central processing unit" term has been in use since as early as 1955. Since

545-456: A SIMD engine and Picochip with 300 processors on a single die, focused on communication applications. In heterogeneous computing , where a system uses more than one kind of processor or cores, multi-core solutions are becoming more common: Xilinx Zynq UltraScale+ MPSoC has a quad-core ARM Cortex-A53 and dual-core ARM Cortex-R5. Software solutions such as OpenAMP are being used to help with inter-processor communication. Mobile devices may use

654-451: A big factor in mobile devices that operate on batteries. Since each core in a multi-core CPU is generally more energy-efficient, the chip becomes more efficient than having a single large monolithic core. This allows higher performance with less energy. A challenge in this, however, is the additional overhead of writing parallel code. Maximizing the usage of the computing resources provided by multi-core processors requires adjustments both to

763-402: A cache had only one level of cache; unlike later level 1 caches, it was not split into L1d (for data) and L1i (for instructions). Almost all current CPUs with caches have a split L1 cache. They also have L2 caches and, for larger processors, L3 caches as well. The L2 cache is usually not split and acts as a common repository for the already split L1 cache. Every core of a multi-core processor has

872-400: A code from the control unit indicating which operation to perform. Depending on the instruction being executed, the operands may come from internal CPU registers , external memory, or constants generated by the ALU itself. When all input signals have settled and propagated through the ALU circuitry, the result of the performed operation appears at the ALU's outputs. The result consists of both

981-413: A combination of cores. Embedded computing operates in an area of processor technology distinct from that of "mainstream" PCs. The same technological drives towards multi-core apply here too. Indeed, in many cases the application is a "natural" fit for multi-core technologies, if the task can easily be partitioned between the different processors. In addition, embedded software is typically developed for

1090-584: A comparable or better level than their synchronous counterparts, it is evident that they do at least excel in simpler math operations. This, combined with their excellent power consumption and heat dissipation properties, makes them very suitable for embedded computers . Many modern CPUs have a die-integrated power managing module which regulates on-demand voltage supply to the CPU circuitry allowing it to keep balance between performance and power consumption. Multi-core processor A multi-core processor ( MCP )

1199-412: A data word, which may be stored in a register or memory, and status information that is typically stored in a special, internal CPU register reserved for this purpose. Modern CPUs typically contain more than one ALU to improve performance. The address generation unit (AGU), sometimes also called the address computation unit (ACU), is an execution unit inside the CPU that calculates addresses used by

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1308-458: A dedicated L2 cache and is usually not shared between the cores. The L3 cache, and higher-level caches, are shared between the cores and are not split. An L4 cache is currently uncommon, and is generally on dynamic random-access memory (DRAM), rather than on static random-access memory (SRAM), on a separate die or chip. That was also the case historically with L1, while bigger chips have allowed integration of it and generally all cache levels, with

1417-448: A given time period, since individual signals can be shorter and do not need to be repeated as often. Assuming that the die can physically fit into the package, multi-core CPU designs require much less printed circuit board (PCB) space than do multi-chip SMP designs. Also, a dual-core processor uses slightly less power than two coupled single-core processors, principally because of the decreased power required to drive signals external to

1526-564: A global clock signal. Two notable examples of this are the ARM compliant AMULET and the MIPS R3000 compatible MiniMIPS. Rather than totally removing the clock signal, some CPU designs allow certain portions of the device to be asynchronous, such as using asynchronous ALUs in conjunction with superscalar pipelining to achieve some arithmetic performance gains. While it is not altogether clear whether totally asynchronous designs can perform at

1635-460: A hundred or more gates, was to build them using a metal–oxide–semiconductor (MOS) semiconductor manufacturing process (either PMOS logic , NMOS logic , or CMOS logic). However, some companies continued to build processors out of bipolar transistor–transistor logic (TTL) chips because bipolar junction transistors were faster than MOS chips up until the 1970s (a few companies such as Datapoint continued to build processors out of TTL chips until

1744-513: A large number of cores (rather than having evolved from single core designs) are sometimes referred to as manycore designs, emphasising qualitative differences. The composition and balance of the cores in multi-core architecture show great variety. Some architectures use one core design repeated consistently ("homogeneous"), while others use a mixture of different cores, each optimized for a different, " heterogeneous " role. How multiple cores are implemented and integrated significantly affects both

1853-522: A lot of semiconductor area to caches and instruction-level parallelism to increase performance and to CPU modes to support operating systems and virtualization . Most modern CPUs are implemented on integrated circuit (IC) microprocessors , with one or more CPUs on a single IC chip. Microprocessor chips with multiple CPUs are called multi-core processors . The individual physical CPUs, called processor cores , can also be multithreaded to support CPU-level multithreading. An IC that contains

1962-411: A memory management unit, translating logical addresses into physical RAM addresses, providing memory protection and paging abilities, useful for virtual memory . Simpler processors, especially microcontrollers , usually don't include an MMU. A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average cost (time or energy) to access data from

2071-476: A new abstraction for C++ parallelism called TBB . Other research efforts include the Codeplay Sieve System , Cray's Chapel , Sun's Fortress , and IBM's X10 . Multi-core processing has also affected the ability of modern computational software development. Developers programming in newer languages might find that their modern languages do not support multi-core functionality. This then requires

2180-459: A number that identifies the address of the next instruction to be fetched. After an instruction is fetched, the PC is incremented by the length of the instruction so that it will contain the address of the next instruction in the sequence. Often, the instruction to be fetched must be retrieved from relatively slow memory, causing the CPU to stall while waiting for the instruction to be returned. This issue

2289-405: A perceived lack of motivation for writing consumer-level threaded applications because of the relative rarity of consumer-level demand for maximum use of computer hardware. Also, serial tasks like decoding the entropy encoding algorithms used in video codecs are impossible to parallelize because each result generated is used to help create the next result of the entropy decoding algorithm. Given

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2398-793: A single FPGA . Each "core" can be considered a " semiconductor intellectual property core " as well as a CPU core. While manufacturing technology improves, reducing the size of individual gates, physical limits of semiconductor -based microelectronics have become a major design concern. These physical limitations can cause significant heat dissipation and data synchronization problems. Various other methods are used to improve CPU performance. Some instruction-level parallelism (ILP) methods such as superscalar pipelining are suitable for many applications, but are inefficient for others that contain difficult-to-predict code. Many applications are better suited to thread-level parallelism (TLP) methods, and multiple independent CPUs are commonly used to increase

2507-532: A single cost-reduced chip. It also contains a "front side bus replacement block" that connects the CPU and GPU internally in exactly the same manner as the front side bus would have done when the CPU and GPU were separate chips, so that the XCGPU doesn't change the hardware characteristics of the Xbox 360. XCGPU contains 372 million transistors and is manufactured by GlobalFoundries on a 45 nm process. Compared to

2616-453: A single die with a unified cache, hence any two working dual-core dies can be used, as opposed to producing four cores on a single die and requiring all four to work to produce a quad-core CPU. From an architectural point of view, ultimately, single CPU designs may make better use of the silicon surface area than multiprocessing cores, so a development commitment to this architecture may carry the risk of obsolescence. Finally, raw processing power

2725-543: A single physical package. Designers may couple cores in a multi-core device tightly or loosely. For example, cores may or may not share caches , and they may implement message passing or shared-memory inter-core communication methods. Common network topologies used to interconnect cores include bus , ring , two-dimensional mesh , and crossbar . Homogeneous multi-core systems include only identical cores; heterogeneous multi-core systems have cores that are not identical (e.g. big.LITTLE have heterogeneous cores that share

2834-565: A specific hardware release, making issues of software portability , legacy code or supporting independent developers less critical than is the case for PC or enterprise computing. As a result, it is easier for developers to adopt new technologies and as a result there is a greater variety of multi-core processing architectures and suppliers. As of 2010 , multi-core network processors have become mainstream, with companies such as Freescale Semiconductor , Cavium Networks , Wintegra and Broadcom all manufacturing products with eight processors. For

2943-413: A system's overall TLP. A combination of increased available space (due to refined manufacturing processes) and the demand for increased TLP led to the development of multi-core CPUs. Several business motives drive the development of multi-core architectures. For decades, it was possible to improve performance of a CPU by shrinking the area of the integrated circuit (IC), which reduced the cost per device on

3052-554: A time. Some CPU architectures include multiple AGUs so more than one address-calculation operation can be executed simultaneously, which brings further performance improvements due to the superscalar nature of advanced CPU designs. For example, Intel incorporates multiple AGUs into its Sandy Bridge and Haswell microarchitectures , which increase bandwidth of the CPU memory subsystem by allowing multiple memory-access instructions to be executed in parallel. Many microprocessors (in smartphones and desktop, laptop, server computers) have

3161-446: A useful computer requires thousands or tens of thousands of switching devices. The overall speed of a system is dependent on the speed of the switches. Vacuum-tube computers such as EDVAC tended to average eight hours between failures, whereas relay computers—such as the slower but earlier Harvard Mark I —failed very rarely. In the end, tube-based CPUs became dominant because the significant speed advantages afforded generally outweighed

3270-399: A variety of specialty cores to run modular software scheduled by a high-level applications programming interface. [...] Atsushi Hasegawa, a senior chief engineer at Renesas , generally agreed. He suggested the cellphone's use of many specialty cores working in concert is a good model for future multi-core designs. [...] Anant Agarwal , founder and chief executive of startup Tilera , took

3379-439: A very small number of ICs; usually just one. The overall smaller CPU size, as a result of being implemented on a single die, means faster switching time because of physical factors like decreased gate parasitic capacitance . This has allowed synchronous microprocessors to have clock rates ranging from tens of megahertz to several gigahertz. Additionally, the ability to construct exceedingly small transistors on an IC has increased

Xenon (processor) - Misplaced Pages Continue

3488-451: Is a microprocessor on a single integrated circuit (IC) with two or more separate central processing units (CPUs), called cores to emphasize their multiplicity (for example, dual-core or quad-core ). Each core reads and executes program instructions , specifically ordinary CPU instructions (such as add, move data, and branch). However, the MCP can run instructions on separate cores at

3597-510: Is a significant ongoing topic of research. Cointegration of multiprocessor applications provides flexibility in network architecture design. Adaptability within parallel models is an additional feature of systems utilizing these protocols. In the consumer market, dual-core processors (that is, microprocessors with two units) started becoming commonplace on personal computers in the late 2000s. Quad-core processors were also being adopted in that era for higher-end systems before becoming standard. In

3706-854: Is based on IBM PowerPC instruction set architecture . It consists of three independent processor cores on a single die. These cores are slightly modified versions of the PPE in the Cell processor used on the PlayStation 3 . Each core has two symmetric hardware threads ( SMT ), for a total of six hardware threads available to games. Each individual core also includes 32 KB of L1 instruction cache and 32 KB of L1 data cache. The XCPU processors were manufactured at IBM's East Fishkill, New York fabrication plant and Chartered Semiconductor Manufacturing (now part of GlobalFoundries ) in Singapore. Chartered reduced

3815-400: Is defined by the CPU's instruction set architecture (ISA). Often, one group of bits (that is, a "field") within the instruction, called the opcode, indicates which operation is to be performed, while the remaining fields usually provide supplemental information required for the operation, such as the operands. Those operands may be specified as a constant value (called an immediate value), or as

3924-421: Is described by Amdahl's law . In the best case, so-called embarrassingly parallel problems may realize speedup factors near the number of cores, or even more if the problem is split up enough to fit within each core's cache(s), avoiding use of much slower main-system memory. Most applications, however, are not accelerated as much unless programmers invest effort in refactoring . The parallelization of software

4033-494: Is generally referred to as the " classic RISC pipeline ", which is quite common among the simple CPUs used in many electronic devices (often called microcontrollers). It largely ignores the important role of CPU cache, and therefore the access stage of the pipeline. Some instructions manipulate the program counter rather than producing result data directly; such instructions are generally called "jumps" and facilitate program behavior like loops , conditional program execution (through

4142-483: Is greater or whether they are equal; one of these flags could then be used by a later jump instruction to determine program flow. Fetch involves retrieving an instruction (which is represented by a number or sequence of numbers) from program memory. The instruction's location (address) in program memory is determined by the program counter (PC; called the "instruction pointer" in Intel x86 microprocessors ), which stores

4251-400: Is largely addressed in modern processors by caches and pipeline architectures (see below). The instruction that the CPU fetches from memory determines what the CPU will do. In the decode step, performed by binary decoder circuitry known as the instruction decoder , the instruction is converted into signals that control other parts of the CPU. The way in which the instruction is interpreted

4360-530: Is most often credited with the design of the stored-program computer because of his design of EDVAC, and the design became known as the von Neumann architecture , others before him, such as Konrad Zuse , had suggested and implemented similar ideas. The so-called Harvard architecture of the Harvard Mark I , which was completed before EDVAC, also used a stored-program design using punched paper tape rather than electronic memory. The key difference between

4469-630: Is not the only constraint on system performance. Two processing cores sharing the same system bus and memory bandwidth limits the real-world performance advantage. The trend in processor development has been towards an ever-increasing number of cores, as processors with hundreds or even thousands of cores become theoretically possible. In addition, multi-core chips mixed with simultaneous multithreading , memory-on-chip, and special-purpose "heterogeneous" (or asymmetric) cores promise further performance and efficiency gains, especially in processing multimedia, recognition and networking applications. For example,

Xenon (processor) - Misplaced Pages Continue

4578-636: Is the IBM PowerPC -based Xenon used in the Xbox 360 ; this reduces the power requirements of the Xbox 360. Another method of addressing some of the problems with a global clock signal is the removal of the clock signal altogether. While removing the global clock signal makes the design process considerably more complex in many ways, asynchronous (or clockless) designs carry marked advantages in power consumption and heat dissipation in comparison with similar synchronous designs. While somewhat uncommon, entire asynchronous CPUs have been built without using

4687-488: The IBM z13 has a 96 KiB L1 instruction cache. Most CPUs are synchronous circuits , which means they employ a clock signal to pace their sequential operations. The clock signal is produced by an external oscillator circuit that generates a consistent number of pulses each second in the form of a periodic square wave . The frequency of the clock pulses determines the rate at which a CPU executes instructions and, consequently,

4796-546: The Manchester Mark 1 ran its first program during the night of 16–17 June 1949. Early CPUs were custom designs used as part of a larger and sometimes distinctive computer. However, this method of designing custom CPUs for a particular application has largely given way to the development of multi-purpose processors produced in large quantities. This standardization began in the era of discrete transistor mainframes and minicomputers , and has rapidly accelerated with

4905-474: The main memory . A cache is a smaller, faster memory, closer to a processor core , which stores copies of the data from frequently used main memory locations . Most CPUs have different independent caches, including instruction and data caches , where the data cache is usually organized as a hierarchy of more cache levels (L1, L2, L3, L4, etc.). All modern (fast) CPUs (with few specialized exceptions ) have multiple levels of CPU caches. The first CPUs that used

5014-492: The operating system (OS) support and to existing application software. Also, the ability of multi-core processors to increase application performance depends on the use of multiple threads within applications. Integration of a multi-core chip can lower the chip production yields. They are also more difficult to manage thermally than lower-density single-core designs. Intel has partially countered this first problem by creating its quad-core designs by combining two dual-core ones on

5123-732: The same integrated circuit die ; separate microprocessor dies in the same package are generally referred to by another name, such as multi-chip module . This article uses the terms "multi-core" and "dual-core" for CPUs manufactured on the same integrated circuit, unless otherwise noted. In contrast to multi-core systems, the term multi-CPU refers to multiple physically separate processing-units (which often contain special circuitry to facilitate communication between each other). The terms many-core and massively multi-core are sometimes used to describe multi-core architectures with an especially high number of cores (tens to thousands ). Some systems use many soft microprocessor cores placed on

5232-453: The AGU, various address-generation calculations can be offloaded from the rest of the CPU, and can often be executed quickly in a single CPU cycle. Capabilities of an AGU depend on a particular CPU and its architecture . Thus, some AGUs implement and expose more address-calculation operations, while some also include more advanced specialized instructions that can operate on multiple operands at

5341-431: The ALU's output word size), an arithmetic overflow flag will be set, influencing the next operation. Hardwired into a CPU's circuitry is a set of basic operations it can perform, called an instruction set . Such operations may involve, for example, adding or subtracting two numbers, comparing two numbers, or jumping to a different part of a program. Each instruction is represented by a unique combination of bits , known as

5450-468: The CPU can fetch the data from actual memory locations. Those address-generation calculations involve different integer arithmetic operations , such as addition, subtraction, modulo operations , or bit shifts . Often, calculating a memory address involves more than one general-purpose machine instruction, which do not necessarily decode and execute quickly. By incorporating an AGU into a CPU design, together with introducing specialized instructions that use

5559-479: The CPU to access main memory . By having address calculations handled by separate circuitry that operates in parallel with the rest of the CPU, the number of CPU cycles required for executing various machine instructions can be reduced, bringing performance improvements. While performing various operations, CPUs need to calculate memory addresses required for fetching data from the memory; for example, in-memory positions of array elements must be calculated before

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5668-422: The CPU to malfunction. Another major issue, as clock rates increase dramatically, is the amount of heat that is dissipated by the CPU . The constantly changing clock causes many components to switch regardless of whether they are being used at that time. In general, a component that is switching uses more energy than an element in a static state. Therefore, as clock rate increases, so does energy consumption, causing

5777-467: The CPU to require more heat dissipation in the form of CPU cooling solutions. One method of dealing with the switching of unneeded components is called clock gating , which involves turning off the clock signal to unneeded components (effectively disabling them). However, this is often regarded as difficult to implement and therefore does not see common usage outside of very low-power designs. One notable recent CPU design that uses extensive clock gating

5886-506: The IC. Alternatively, for the same circuit area, more transistors could be used in the design, which increased functionality, especially for complex instruction set computing (CISC) architectures. Clock rates also increased by orders of magnitude in the decades of the late 20th century, from several megahertz in the 1980s to several gigahertz in the early 2000s. As the rate of clock speed improvements slowed, increased use of parallel computing in

5995-431: The advent and eventual success of the ubiquitous personal computer , the term CPU is now applied almost exclusively to microprocessors. Several CPUs (denoted cores ) can be combined in a single processing chip. Previous generations of CPUs were implemented as discrete components and numerous small integrated circuits (ICs) on one or more circuit boards. Microprocessors, on the other hand, are CPUs manufactured on

6104-428: The advent of the transistor . Transistorized CPUs during the 1950s and 1960s no longer had to be built out of bulky, unreliable, and fragile switching elements, like vacuum tubes and relays . With this improvement, more complex and reliable CPUs were built onto one or several printed circuit boards containing discrete (individual) components. In 1964, IBM introduced its IBM System/360 computer architecture that

6213-662: The alternatives. An especially strong contender for established markets is the further integration of peripheral functions into the chip. The proximity of multiple CPU cores on the same die allows the cache coherency circuitry to operate at a much higher clock rate than what is possible if the signals have to travel off-chip. Combining equivalent CPUs on a single die significantly improves the performance of cache snoop (alternative: Bus snooping ) operations. Put simply, this means that signals between different CPUs travel shorter distances, and therefore those signals degrade less. These higher-quality signals allow more data to be sent in

6322-535: The chip. Furthermore, the cores share some circuitry, like the L2 cache and the interface to the front-side bus (FSB). In terms of competing technologies for the available silicon die area, multi-core design can make use of proven CPU core library designs and produce a product with lower risk of design error than devising a new wider-core design. Also, adding more cache suffers from diminishing returns. Multi-core chips also allow higher performance at lower energy. This can be

6431-564: The complexity and number of transistors in a single CPU many fold. This widely observed trend is described by Moore's law , which had proven to be a fairly accurate predictor of the growth of CPU (and other IC) complexity until 2016. While the complexity, size, construction and general form of CPUs have changed enormously since 1950, the basic design and function has not changed much at all. Almost all common CPUs today can be very accurately described as von Neumann stored-program machines. As Moore's law no longer holds, concerns have arisen about

6540-423: The complexity scale, a machine language program is a collection of machine language instructions that the CPU executes. The actual mathematical operation for each instruction is performed by a combinational logic circuit within the CPU's processor known as the arithmetic–logic unit or ALU. In general, a CPU executes an instruction by fetching it from memory, using its ALU to perform an operation, and then storing

6649-486: The control unit as part of the von Neumann architecture . In modern computer designs, the control unit is typically an internal part of the CPU with its overall role and operation unchanged since its introduction. The arithmetic logic unit (ALU) is a digital circuit within the processor that performs integer arithmetic and bitwise logic operations. The inputs to the ALU are the data words to be operated on (called operands ), status information from previous operations, and

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6758-430: The count can go over 10 million (and in one case up to 20 million processing elements total in addition to host processors). The improvement in performance gained by the use of a multi-core processor depends very much on the software algorithms used and their implementation. In particular, possible gains are limited by the fraction of the software that can run in parallel simultaneously on multiple cores; this effect

6867-453: The desired operation. The action is then completed, typically in response to a clock pulse. Very often the results are written to an internal CPU register for quick access by subsequent instructions. In other cases results may be written to slower, but less expensive and higher capacity main memory . For example, if an instruction that performs addition is to be executed, registers containing operands (numbers to be summed) are activated, as are

6976-507: The developer's programming skills and the consumer's expectations of apps and interactivity versus the device. A device advertised as being octa-core will only have independent cores if advertised as True Octa-core , or similar styling, as opposed to being merely two sets of quad-cores each with fixed clock speeds. The article "CPU designers debate multi-core future" by Rick Merritt, EE Times 2008, includes these comments: Chuck Moore [...] suggested computers should be like cellphones, using

7085-429: The drawbacks of globally synchronous CPUs. For example, a clock signal is subject to the delays of any other electrical signal. Higher clock rates in increasingly complex CPUs make it more difficult to keep the clock signal in phase (synchronized) throughout the entire unit. This has led many modern CPUs to require multiple identical clock signals to be provided to avoid delaying a single signal significantly enough to cause

7194-453: The early 1980s). In the 1960s, MOS ICs were slower and initially considered useful only in applications that required low power. Following the development of silicon-gate MOS technology by Federico Faggin at Fairchild Semiconductor in 1968, MOS ICs largely replaced bipolar TTL as the standard chip technology in the early 1970s. As the microelectronic technology advanced, an increasing number of transistors were placed on ICs, decreasing

7303-578: The era of specialized supercomputers like those made by Cray Inc and Fujitsu Ltd . During this period, a method of manufacturing many interconnected transistors in a compact space was developed. The integrated circuit (IC) allowed a large number of transistors to be manufactured on a single semiconductor -based die , or "chip". At first, only very basic non-specialized digital circuits such as NOR gates were miniaturized into ICs. CPUs based on these "building block" ICs are generally referred to as "small-scale integration" (SSI) devices. SSI ICs, such as

7412-503: The execution of an instruction, the entire process repeats, with the next instruction cycle normally fetching the next-in-sequence instruction because of the incremented value in the program counter . If a jump instruction was executed, the program counter will be modified to contain the address of the instruction that was jumped to and program execution continues normally. In more complex CPUs, multiple instructions can be fetched, decoded and executed simultaneously. This section describes what

7521-578: The fabrication process in 2007 to 65 nm from 90 nm , thus reducing manufacturing costs for Microsoft. The Xbox 360 S introduced the XCGPU (codename Vejle), which integrated the Xenon CPU and the Xenos GPU onto the same die, and the eDRAM into the same package. The XCGPU follows the trend started with the integrated EE+GS in PlayStation 2 Slimline , combining CPU, GPU, memory controllers and IO in

7630-401: The faster the clock, the more instructions the CPU will execute each second. To ensure proper operation of the CPU, the clock period is longer than the maximum time needed for all signals to propagate (move) through the CPU. In setting the clock period to a value well above the worst-case propagation delay , it is possible to design the entire CPU and the way it moves data around the "edges" of

7739-457: The form of multi-core processors has been pursued to improve overall processing performance. Multiple cores were used on the same CPU chip, which could then lead to better sales of CPU chips with two or more cores. For example, Intel has produced a 48-core processor for research in cloud computing; each core has an x86 architecture. Since computer manufacturers have long implemented symmetric multiprocessing (SMP) designs using discrete CPUs,

7848-416: The increasing emphasis on multi-core chip design, stemming from the grave thermal and power consumption problems posed by any further significant increase in processor clock speeds, the extent to which software can be multithreaded to take advantage of these new chips is likely to be the single greatest constraint on computer performance in the future. If developers are unable to design software to fully exploit

7957-559: The individual transistors used by the PDP-8 and PDP-10 to SSI ICs, and their extremely popular PDP-11 line was originally built with SSI ICs, but was eventually implemented with LSI components once these became practical. Lee Boysel published influential articles, including a 1967 "manifesto", which described how to build the equivalent of a 32-bit mainframe computer from a relatively small number of large-scale integration circuits (LSI). The only way to build LSI chips, which are chips with

8066-457: The issues regarding implementing multi-core processor architecture and supporting it with software are well known. Additionally: In order to continue delivering regular performance improvements for general-purpose processors, manufacturers such as Intel and AMD have turned to multi-core designs, sacrificing lower manufacturing-costs for higher performance in some applications and systems. Multi-core architectures are being developed, but so are

8175-443: The late 2010s, hexa-core (six cores) started entering the mainstream and since the early 2020s has overtaken quad-core in many spaces. The terms multi-core and dual-core most commonly refer to some sort of central processing unit (CPU), but are sometimes also applied to digital signal processors (DSP) and system on a chip (SoC). The terms are generally used only to refer to multi-core microprocessors that are manufactured on

8284-439: The limits of integrated circuit transistor technology. Extreme miniaturization of electronic gates is causing the effects of phenomena like electromigration and subthreshold leakage to become much more significant. These newer concerns are among the many factors causing researchers to investigate new methods of computing such as the quantum computer , as well as to expand the use of parallelism and other methods that extend

8393-408: The location of a value that may be a processor register or a memory address, as determined by some addressing mode . In some CPU designs, the instruction decoder is implemented as a hardwired, unchangeable binary decoder circuit. In others, a microprogram is used to translate instructions into sets of CPU configuration signals that are applied sequentially over multiple clock pulses. In some cases

8502-406: The machine language opcode . While processing an instruction, the CPU decodes the opcode (via a binary decoder ) into control signals, which orchestrate the behavior of the CPU. A complete machine language instruction consists of an opcode and, in many cases, additional bits that specify arguments for the operation (for example, the numbers to be summed in the case of an addition operation). Going up

8611-421: The memory that stores the microprogram is rewritable, making it possible to change the way in which the CPU decodes instructions. After the fetch and decode steps, the execute step is performed. Depending on the CPU architecture, this may consist of a single action or a sequence of actions. During each action, control signals electrically enable or disable various parts of the CPU so they can perform all or part of

8720-710: The number of individual ICs needed for a complete CPU. MSI and LSI ICs increased transistor counts to hundreds, and then thousands. By 1968, the number of ICs required to build a complete CPU had been reduced to 24 ICs of eight different types, with each IC containing roughly 1000 MOSFETs. In stark contrast with its SSI and MSI predecessors, the first LSI implementation of the PDP-11 contained a CPU composed of only four LSI integrated circuits. Since microprocessors were first introduced they have almost completely overtaken all other central processing unit implementation methods. The first commercially available microprocessor, made in 1971,

8829-583: The ones used in the Apollo Guidance Computer , usually contained up to a few dozen transistors. To build an entire CPU out of SSI ICs required thousands of individual chips, but still consumed much less space and power than earlier discrete transistor designs. IBM's System/370 , follow-on to the System/360, used SSI ICs rather than Solid Logic Technology discrete-transistor modules. DEC's PDP-8 /I and KI10 PDP-10 also switched from

8938-497: The operating system of the network device. In digital signal processing the same trend applies: Texas Instruments has the three-core TMS320C6488 and four-core TMS320C5441, Freescale the four-core MSC8144 and six-core MSC8156 (and both have stated they are working on eight-core successors). Newer entries include the Storm-1 family from Stream Processors, Inc with 40 and 80 general purpose ALUs per chip, all programmable in C as

9047-408: The opposing view. He said multi-core chips need to be homogeneous collections of general-purpose cores to keep the software model simple. An outdated version of an anti-virus application may create a new thread for a scan process, while its GUI thread waits for commands from the user (e.g. cancel the scan). In such cases, a multi-core architecture is of little benefit for the application itself due to

9156-664: The original chipset in the Xbox 360 the combined power requirements are reduced by 60% and the physical chip area by 50%. In 2014, the Winchester Xbox 360 system introduced a shrunken XCGPU on a 32 nm process (codename Oban). This chip is no longer a multi-chip-module and integrates the eDRAM into the main die. Illustrations of the different generations of processors in Xbox 360 and Xbox 360 S. Central processing unit The form, design , and implementation of CPUs have changed over time, but their fundamental operation remains almost unchanged. Principal components of

9265-418: The other hand, on the server side , multi-core processors are ideal because they allow many users to connect to a site simultaneously and have independent threads of execution. This allows for Web servers and application servers that have much better throughput . Vendors may license some software "per processor". This can give rise to ambiguity, because a "processor" may consist either of a single core or of

9374-409: The parts of the arithmetic logic unit (ALU) that perform addition. When the clock pulse occurs, the operands flow from the source registers into the ALU, and the sum appears at its output. On subsequent clock pulses, other components are enabled (and disabled) to move the output (the sum of the operation) to storage (e.g., a register or memory). If the resulting sum is too large (i.e., it is larger than

9483-544: The physical wiring of the computer. This overcame a severe limitation of ENIAC, which was the considerable time and effort required to reconfigure the computer to perform a new task. With von Neumann's design, the program that EDVAC ran could be changed simply by changing the contents of the memory. EDVAC was not the first stored-program computer; the Manchester Baby , which was a small-scale experimental stored-program computer, ran its first program on 21 June 1948 and

9592-501: The popularization of the integrated circuit (IC). The IC has allowed increasingly complex CPUs to be designed and manufactured to tolerances on the order of nanometers . Both the miniaturization and standardization of CPUs have increased the presence of digital devices in modern life far beyond the limited application of dedicated computing machines. Modern microprocessors appear in electronic devices ranging from automobiles to cellphones, and sometimes even in toys. While von Neumann

9701-473: The possible exception of the last level. Each extra level of cache tends to be bigger and is optimized differently. Other types of caches exist (that are not counted towards the "cache size" of the most important caches mentioned above), such as the translation lookaside buffer (TLB) that is part of the memory management unit (MMU) that most CPUs have. Caches are generally sized in powers of two: 2, 8, 16 etc. KiB or MiB (for larger non-L1) sizes, although

9810-488: The problem, for example using a coordination language and program building blocks (programming libraries or higher-order functions). Each block can have a different native implementation for each processor type. Users simply program using these abstractions and an intelligent compiler chooses the best implementation based on the context. Managing concurrency acquires a central role in developing parallel applications. The basic steps in designing parallel applications are: On

9919-451: The processor. It tells the computer's memory, arithmetic and logic unit and input and output devices how to respond to the instructions that have been sent to the processor. It directs the operation of the other units by providing timing and control signals. Most computer resources are managed by the CU. It directs the flow of data between the CPU and the other devices. John von Neumann included

10028-478: The reliability problems. Most of these early synchronous CPUs ran at low clock rates compared to modern microelectronic designs. Clock signal frequencies ranging from 100 kHz to 4 MHz were very common at this time, limited largely by the speed of the switching devices they were built with. The design complexity of CPUs increased as various technologies facilitated the building of smaller and more reliable electronic devices. The first such improvement came with

10137-735: The resources provided by multiple cores, then they will ultimately reach an insurmountable performance ceiling. The telecommunications market had been one of the first that needed a new design of parallel datapath packet processing because there was a very quick adoption of these multiple-core processors for the datapath and the control plane. These MPUs are going to replace the traditional Network Processors that were based on proprietary microcode or picocode . Parallel programming techniques can benefit from multiple cores directly. Some existing parallel programming models such as Cilk Plus , OpenMP , OpenHMPP , FastFlow , Skandium, MPI , and Erlang can be used on multi-core platforms. Intel introduced

10246-409: The result to memory. Besides the instructions for integer mathematics and logic operations, various other machine instructions exist, such as those for loading data from memory and storing it back, branching operations, and mathematical operations on floating-point numbers performed by the CPU's floating-point unit (FPU). The control unit (CU) is a component of the CPU that directs the operation of

10355-484: The rising and falling clock signal. This has the advantage of simplifying the CPU significantly, both from a design perspective and a component-count perspective. However, it also carries the disadvantage that the entire CPU must wait on its slowest elements, even though some portions of it are much faster. This limitation has largely been compensated for by various methods of increasing CPU parallelism (see below). However, architectural improvements alone do not solve all of

10464-587: The same instruction set , while AMD Accelerated Processing Units have cores that do not share the same instruction set). Just as with single-processor systems, cores in multi-core systems may implement architectures such as VLIW , superscalar , vector , or multithreading . Multi-core processors are widely used across many application domains, including general-purpose , embedded , network , digital signal processing (DSP), and graphics (GPU). Core count goes up to even dozens, and for specialized chips over 10,000, and in supercomputers (i.e. clusters of chips)

10573-432: The same time, increasing overall speed for programs that support multithreading or other parallel computing techniques. Manufacturers typically integrate the cores onto a single IC die , known as a chip multiprocessor (CMP), or onto multiple dies in a single chip package . As of 2024, the microprocessors used in almost all new personal computers are multi-core. A multi-core processor implements multiprocessing in

10682-540: The short switching time of a transistor in comparison to a tube or relay. The increased reliability and dramatically increased speed of the switching elements, which were almost exclusively transistors by this time; CPU clock rates in the tens of megahertz were easily obtained during this period. Additionally, while discrete transistor and IC CPUs were in heavy usage, new high-performance designs like single instruction, multiple data (SIMD) vector processors began to appear. These early experimental designs later gave rise to

10791-462: The single thread doing all the heavy lifting and the inability to balance the work evenly across multiple cores. Programming truly multithreaded code often requires complex co-ordination of threads and can easily introduce subtle and difficult-to-find bugs due to the interweaving of processing on data shared between threads (see thread-safety ). Consequently, such code is much more difficult to debug than single-threaded code when it breaks. There has been

10900-404: The system developer, a key challenge is how to exploit all the cores in these devices to achieve maximum networking performance at the system level, despite the performance limitations inherent in a symmetric multiprocessing (SMP) operating system. Companies such as 6WIND provide portable packet processing software designed so that the networking data plane runs in a fast path environment outside

11009-439: The term "CPU" is generally defined as a device for software (computer program) execution, the earliest devices that could rightly be called CPUs came with the advent of the stored-program computer . The idea of a stored-program computer had been already present in the design of John Presper Eckert and John William Mauchly 's ENIAC , but was initially omitted so that it could be finished sooner. On June 30, 1945, before ENIAC

11118-463: The use of numerical libraries to access code written in languages like C and Fortran , which perform math computations faster than newer languages like C# . Intel's MKL and AMD's ACML are written in these native languages and take advantage of multi-core processing. Balancing the application workload across processors can be problematic, especially if they have different performance characteristics. There are different conceptual models to deal with

11227-422: The use of a conditional jump), and existence of functions . In some processors, some other instructions change the state of bits in a "flags" register . These flags can be used to influence how a program behaves, since they often indicate the outcome of various operations. For example, in such processors a "compare" instruction evaluates two values and sets or clears bits in the flags register to indicate which one

11336-431: The usefulness of the classical von Neumann model. The fundamental operation of most CPUs, regardless of the physical form they take, is to execute a sequence of stored instructions that is called a program. The instructions to be executed are kept in some kind of computer memory . Nearly all CPUs follow the fetch, decode and execute steps in their operation, which are collectively known as the instruction cycle . After

11445-616: The von Neumann and Harvard architectures is that the latter separates the storage and treatment of CPU instructions and data, while the former uses the same memory space for both. Most modern CPUs are primarily von Neumann in design, but CPUs with the Harvard architecture are seen as well, especially in embedded applications; for instance, the Atmel AVR microcontrollers are Harvard-architecture processors. Relays and vacuum tubes (thermionic tubes) were commonly used as switching elements;

11554-538: Was made, mathematician John von Neumann distributed a paper entitled First Draft of a Report on the EDVAC . It was the outline of a stored-program computer that would eventually be completed in August 1949. EDVAC was designed to perform a certain number of instructions (or operations) of various types. Significantly, the programs written for EDVAC were to be stored in high-speed computer memory rather than specified by

11663-598: Was so popular that it dominated the mainframe computer market for decades and left a legacy that is continued by similar modern computers like the IBM zSeries . In 1965, Digital Equipment Corporation (DEC) introduced another influential computer aimed at the scientific and research markets—the PDP-8 . Transistor-based computers had several distinct advantages over their predecessors. Aside from facilitating increased reliability and lower power consumption, transistors also allowed CPUs to operate at much higher speeds because of

11772-399: Was the Intel 4004 , and the first widely used microprocessor, made in 1974, was the Intel 8080 . Mainframe and minicomputer manufacturers of the time launched proprietary IC development programs to upgrade their older computer architectures , and eventually produced instruction set compatible microprocessors that were backward-compatible with their older hardware and software. Combined with

11881-429: Was used in a series of computers capable of running the same programs with different speeds and performances. This was significant at a time when most electronic computers were incompatible with one another, even those made by the same manufacturer. To facilitate this improvement, IBM used the concept of a microprogram (often called "microcode"), which still sees widespread use in modern CPUs. The System/360 architecture

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