query: what cycle does the cpu carry out continuously to process instructions

pos: Instruction cycle Instruction cycle The instruction cycle (also known as the fetch–decode–execute cycle or the fetch-execute cycle) is the basic operational process of a computer system. It is the process by which a computer retrieves a program instruction from its memory, determines what actions the instruction describes, and then carries out those actions. This cycle is repeated continuously by a computer's central processing unit (CPU), from boot-up until the computer has shut down. In simpler CPUs the instruction cycle is executed sequentially, each instruction being processed before the next one is started. In most modern CPUs the instruction cycles are instead executed

pos: Instruction unit Instruction unit The instruction unit (IU) in a central processing unit (CPU) is responsible for organising program instructions to be fetched from memory, and executed, in an appropriate order. It is a part of the control unit, which in turn is part of the CPU. In the simplest style of computer architecture, the instruction cycle is very rigid, and runs exactly as specified by the programmer. In the Instruction Fetch part of the cycle, the contents of the program counter (PC) register are placed on the address bus, and sent to the memory unit; the memory unit returns the instruction

pos: Program counter call. In a typical central processing unit (CPU), the PC is a digital counter (which is the origin of the term "program counter") that may be one of many registers in the CPU hardware. The instruction cycle begins with a fetch, in which the CPU places the value of the PC on the address bus to send it to the memory. The memory responds by sending the contents of that memory location on the data bus. (This is the stored-program computer model, in which executable instructions are stored alongside ordinary data in memory, and handled identically by it). Following the

neg: Bitboard less effective and potentially reduces the number of instructions the processor can execute per cycle. Many bitboard operations require fewer conditionals and therefore increase pipelining and make effective use of multiple execution units on many CPUs. CPUs have a bit width which they are designed toward and can carry out bitwise operations in one cycle in this width. So, on a 64-bit or more CPU, 64-bit operations can occur in one instruction. There may be support for higher or lower width instructions. Many 32-bit CPUs may have some 64-bit instructions and those may take more than one cycle or otherwise

neg: Instruction cycle set of instructions in read-only memory (ROM), which begins the process of loading (or "booting") the operating system. The fetch step is the same for each instruction: The control unit fetches the instruction's address from the memory unit. The decoding process allows the CPU to determine what instruction is to be performed so that the CPU can tell how many operands it needs to fetch in order to perform the instruction. The opcode fetched from the memory is decoded for the next steps and moved to the appropriate registers. The decoding is done by the CPU's Control Unit. This step

neg: Very long instruction word have four to eight main execution units. Compilers generate initial instruction sequences for the VLIW CPU in roughly the same manner as for traditional CPUs, generating a sequence of RISC-like instructions. The compiler analyzes this code for dependence relationships and resource requirements. It then schedules the instructions according to those constraints. In this process, independent instructions can be scheduled in parallel. Because VLIWs typically represent instructions scheduled in parallel with a longer instruction word that incorporates the individual instructions, this results in a much longer opcode (termed "very long") to specify what executes on a given cycle. Examples of contemporary

neg: Instructions per cycle is important to note that Multithreading does NOT mean that two threads can operate on the same core simultaneously, sharing pipeline resources. Instead, the CPU allows one thread to use the core whilst another waits for data to arrive from memory, as in the case of a Cache miss. The operating system's scheduler can return the original thread to the queue, and then back into the CPU, once the data has been fetched. Thus, this feature does not have any effect on the theoretical floating point performance of a CPU, but, in certain cases, can help the CPU come closer

neg: Superscalar processor these units fed with instructions, the performance of the system will be no better than that of a simpler, cheaper design. A superscalar processor usually sustains an execution rate in excess of one instruction per machine cycle. But merely processing multiple instructions concurrently does not make an architecture superscalar, since pipelined, multiprocessor or multi-core architectures also achieve that, but with different methods. In a superscalar CPU the dispatcher reads instructions from memory and decides which ones can be run in parallel, dispatching each to one of the several execution units contained inside a single CPU. Therefore, a superscalar processor can

neg: Central processing unit 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 of the CPU contains circuitry that uses electrical signals to direct the entire computer system to carry out stored program instructions. The control unit does not execute program instructions; rather, it directs other parts of the system to do so. The control unit communicates with both the ALU and memory. The arithmetic logic unit (ALU) is a digital circuit

neg: DMS-100 CPU on a cycle by cycle basis. Any discrepancy between the two CPUs results in maintenance circuitry determining which CPU is at fault and activity to change to the same CPU. A Program Store is dedicated to each CPU and is a memory for the program instructions required by that CPU for processing calls, maintenance and for administrative tasks. The PS associated with the other CPU contains identical program instructions. A Data Store is dedicated with each CPU and contains dynamic information on a per-call basis, as well as customer data and office-specific settings. The other CPU is also associated

neg: Barrel processor Barrel processor A barrel processor is a CPU that switches between threads of execution on every cycle. This CPU design technique is also known as "interleaved" or "fine-grained" temporal multithreading. Unlike simultaneous multithreading in modern superscalar architectures, it generally does not allow execution of multiple instructions in one cycle. Like preemptive multitasking, each thread of execution is assigned its own program counter and other hardware registers (each thread's architectural state). A barrel processor can guarantee that each thread will execute one instruction every "n" cycles, unlike a preemptive multitasking machine, that typically runs one thread of execution for tens of

neg: Barrel processor miss or pipeline stall occurs. Advantages to employing barrel processors over single-tasking processors include: There are a few disadvantages to barrel processors. Barrel processor A barrel processor is a CPU that switches between threads of execution on every cycle. This CPU design technique is also known as "interleaved" or "fine-grained" temporal multithreading. Unlike simultaneous multithreading in modern superscalar architectures, it generally does not allow execution of multiple instructions in one cycle. Like preemptive multitasking, each thread of execution is assigned its own program counter and other hardware registers (each thread's architectural state). A barrel processor can guarantee that each thread

neg: CDC 6600 arithmetic unit, rather than discrete "functional units". As such, it could not overlap instructions' execution times. For example, in a 6400 CPU, if an add instruction immediately followed a multiply instruction, the add instruction could not be started till the multiply instruction finished, so the net execution time of the two instructions would be the sum of their individual execution times. The 6600 CPU had multiple functional units which could operate simultaneously, "i.e.", "in parallel", allowing the CPU to overlap instructions' execution times. For example, a 6600 CPU could begin executing an add instruction in the next CPU cycle following

neg: R800 (CPU) bits, so a workaround was needed. The solution used in the R800 was to refresh entire blocks of RAM, instead of refreshing one line of RAM on each instruction issued. Each 30μs, the CPU is halted for 4μs, this time is used to refresh a block of the RAM. Since there's no refresh in between fetch instructions, and the waitstate is removed due to faster RAM chips, simple instructions can be issued using only one cycle. This cycle would be cycle 2 in the Z80 example above; cycle 1 becomes optional, and it's only issued when the program crosses a

neg: Instructions per cycle Instructions per cycle In computer architecture, instructions per cycle (IPC) is one aspect of a processor's performance: the average number of instructions executed for each clock cycle. It is the multiplicative inverse of cycles per instruction. The calculation of IPC is done through running a set piece of code, calculating the number of machine-level instructions required to complete it, then using high-performance timers to calculate the number of clock cycles required to complete it on the actual hardware. The final result comes from dividing the number of instructions by the number of CPU clock cycles. The number of instructions per

neg: TI Advanced Scientific Computer supporting microcoded arithmetic and mathematical instructions that operated on scalars, vectors, or matrices. The vector processing facilities had a memory-to-memory architecture; where the vector operands were read from, and the resulting vector written to, memory. The CPU could be have one, two, or four vector lanes, allowing the CPU to produce one to four vector results every cycle, depending on the number of vector lanes installed. The vector lanes were also used for scalar instructions, and each lane could keep up to 12 scalar instructions in-flight simultaneously. The CPU, with four lanes, allowed up to 36 instructions in total across

neg: Multithreading (computer architecture) superscalar processor issues multiple instructions from a single thread every CPU cycle, in simultaneous multithreading (SMT) a superscalar processor can issue instructions from multiple threads every CPU cycle. Recognizing that any single thread has a limited amount of instruction-level parallelism, this type of multithreading tries to exploit parallelism available across multiple threads to decrease the waste associated with unused issue slots. For example: To distinguish the other types of multithreading from SMT, the term "temporal multithreading" is used to denote when instructions from only one thread can be issued at a time. In addition to the hardware costs discussed for

neg: SpeedStep issue x86 halt (HLT) instructions, which suspend operation of parts of the CPU for a time period, so it uses less energy per tick of the CPU clock than when executing productive instructions in its normal state. For a given rate of work, a CPU running at a higher clock rate will execute a greater proportion of HLT instructions. The simple equation which relates power, voltage and frequency above also does not take into account the static power consumption of the CPU. This tends not to change with frequency, but does change with temperature and voltage. Hot electrons, and electrons

neg: I/O bound of data processing in the core, while the rate at which data is transferred from storage to the processor does not increase with it. As CPU clock speed increases, allowing more instructions to be executed in a given time window, the limiting factor of effective execution is the rate at which instructions can be delivered to the processor from storage, and sent from the processor to their destination. In short, programs naturally shift to being more and more I/O bound. Assume we have one CPU-bound process and many I/O-bound processes. As the processes flow around the system, the following scenario

neg: Computer architecture as CPU design. The exact form of a computer system depends on the constraints and goals. Computer architectures usually trade off standards, power versus performance, cost, memory capacity, latency (latency is the amount of time that it takes for information from one node to travel to the source) and throughput. Sometimes other considerations, such as features, size, weight, reliability, and expandability are also factors. The most common scheme does an in depth power analysis and figures out how to keep power consumption low, while maintaining adequate performance. Modern computer performance is often described in IPC (instructions per cycle). This measures

neg: HAL SPARC64 1996. The SPARC64 is a superscalar microprocessor that issues four instructions per cycle and executes them out of order. It is a multichip design, consisting of seven dies: a CPU die, MMU die, four CACHE dies and a CLOCK die. The CPU die contains the majority of logic, all of the execution units and a level 0 (L0) instruction cache. The execution units consist of two integer units, address units, floating-point units (FPUs), memory units. The FPU hardware consists of a fused multiply add (FMA) unit and a divide unit. But the FMA instructions are really fused (that is, with

neg: Instructions per cycle most architectures, nor do they represent the primary architectural definition of IPC, which measures the number of average scalar instructions retired per cycle, both integer, floating point, and control. To get a theoretical GFLOPS (Billions of FLOPS) rating for a given CPU, multiply the number in this chart by the number of cores and then by the stock clock (in GHz) of a particular CPU model. For example, a Coffee Lake i7-8700K theoretically handles 32 Single-Precision floats per cycle, has 6 cores and a 3.7 GHz base clock. This gives it 32 x 6 x 3.7 = 710.4 GFLOPS. It

neg: Process state are not in the ready queue. A process moves into the running state when it is chosen for execution. The process's instructions are executed by one of the CPUs (or cores) of the system. There is at most one running process per CPU or core. A process can run in either of the two modes, namely "kernel mode" or "user mode". A process transitions to a blocked state when it cannot carry on without an external change in state or event occurring. For example, a process may block on a call to an I/O device such as a printer, if

neg: Central processing unit multithreading, where instructions from multiple threads are executed in parallel within one CPU clock cycle. For several decades from the 1970s to early 2000s, the focus in designing high performance general purpose CPUs was largely on achieving high ILP through technologies such as pipelining, caches, superscalar execution, out-of-order execution, etc. This trend culminated in large, power-hungry CPUs such as the Intel Pentium 4. By the early 2000s, CPU designers were thwarted from achieving higher performance from ILP techniques due to the growing disparity between CPU operating frequencies and main memory operating frequencies as well as escalating CPU power dissipation owing

neg: Oracle VM Server for SPARC "CoolThreads" processors. A single chip contains up to 32 CPU cores, and each core has either four hardware threads (for the UltraSPARC T1) or eight hardware threads (for the UltraSPARC T2/T2+, and SPARC T3/T4 and later) that act as virtual CPUs. All CPU cores execute instructions concurrently, and each core switches between threads—typically when a thread stalls on a cache miss or goes idle—within a single clock cycle. This lets the processor gain throughput that is lost during cache misses in conventional CPU designs. Each domain is assigned its own CPU threads and executes CPU instructions at native speed, avoiding

neg: Superscalar processor dispatched instructions. Even though the instruction stream may contain no inter-instruction dependencies, a superscalar CPU must nonetheless check for that possibility, since there is no assurance otherwise and failure to detect a dependency would produce incorrect results. No matter how advanced the semiconductor process or how fast the switching speed, this places a practical limit on how many instructions can be simultaneously dispatched. While process advances will allow ever greater numbers of execution units (e.g., ALUs), the burden of checking instruction dependencies grows rapidly, as does the complexity of register renaming circuitry to mitigate some dependencies. Collectively the power consumption,

neg: Instructions per second given in kilo Instructions Per Second (kIPS). The most famous was the Gibson Mix, produced by Jack Clark Gibson of IBM for scientific applications. Other ratings, such as the ADP mix which does not include floating point operations, were produced for commercial applications. The thousand instructions per second (kIPS) unit is rarely used today, as most current microprocessors can execute at least a million instructions per second. The speed of a given CPU depends on many factors, such as the type of instructions being executed, the execution order and the presence of branch instructions (problematic in CPU pipelines). CPU instruction

neg: Central processing unit complete before proceeding to the next instruction. As a result, the subscalar CPU gets "hung up" on instructions which take more than one clock cycle to complete execution. Even adding a second execution unit (see below) does not improve performance much; rather than one pathway being hung up, now two pathways are hung up and the number of unused transistors is increased. This design, wherein the CPU's execution resources can operate on only one instruction at a time, can only possibly reach "scalar" performance (one instruction per clock cycle, ). However, the performance is nearly always subscalar (less than one

neg: History of computing hardware tape provided archival capability for this data, at a lower cost than disk. Many second-generation CPUs delegated peripheral device communications to a secondary processor. For example, while the communication processor controlled card reading and punching, the main CPU executed calculations and binary branch instructions. One databus would bear data between the main CPU and core memory at the CPU's fetch-execute cycle rate, and other databusses would typically serve the peripheral devices. On the PDP-1, the core memory's cycle time was 5 microseconds; consequently most arithmetic instructions took 10 microseconds (100,000 operations per second) because most operations took at least two

neg: MP6 the CPU to execute up to three MMX instructions in a single cycle. Its three integer units made it possible to execute three integer instructions in a single cycle as well and the fully pipelined floating point unit could execute up to two floating-point instructions per cycle. To further improve the performance the core utilized branch prediction and a number of techniques to resolve data dependency conflicts. According to Rise, the mP6 should perform almost as fast as Intel Pentium II at the same frequencies. Despite its innovative features, the real-life performance of the mP6 proved disappointing. This was mainly

neg: Bitboard as finding the "first" bit, that make bitboard operations even more efficient. If they do not have instructions well known algorithms can perform some "magic" transformations that do these quickly. Furthermore, modern CPUs have instruction pipelines that queue instructions for execution. A processor with multiple execution units can perform more than one instruction per cycle if more than one instruction is available in the pipeline. Branching (the use of conditionals like if) makes it harder for the processor to fill its pipeline(s) because the CPU cannot tell what it needs to do in advance. Too much branching makes the pipeline

neg: MOS Technology 6502 thereby control the whole "machine"-cycle directly. Typical instructions might take half as many cycles to complete on the 6502 than contemporary designs. Like most simple CPUs of the era, the dynamic NMOS 6502 chip is not sequenced by a microcode ROM but uses a PLA (which occupied about 15 percent of the chip area) for instruction decoding and sequencing. Like most eight-bit microprocessors, the chip does some limited overlapping of fetching and execution. The low clock frequency moderated the speed requirement of memory and peripherals attached to the CPU, as only about 50 percent of the clock cycle was available

neg: Booting be carried out, effectively loading a small number of boot loader instructions into memory; a completion signal from the I/O device may then be used to start execution of the instructions by the CPU. Smaller computers often use less flexible but more automatic boot loader mechanisms to ensure that the computer starts quickly and with a predetermined software configuration. In many desktop computers, for example, the bootstrapping process begins with the CPU executing software contained in ROM (for example, the BIOS of an IBM PC) at a predefined address (some CPUs, including the Intel x86 series are designed to execute

neg: AVR32 AVR32 The AVR32 is a 32-bit RISC microcontroller architecture produced by Atmel. The microcontroller architecture was designed by a handful of people educated at the Norwegian University of Science and Technology, including lead designer Øyvind Strøm and CPU architect Erik Renno in Atmel's Norwegian design center. Most instructions are executed in a single-cycle. The multiply–accumulate unit can perform a 32-bit × 16-bit + 48-bit arithmetic operation in two cycles (result latency), issued once per cycle. It does not resemble the 8-bit AVR microcontroller family, even though they were both designed at Atmel Norway, in Trondheim. Some of the debug-tools are

neg: FLAGS register the FLAGS register. The conditional jump instructions use certain flags to compute. For example, codice_3 uses the zero flag, codice_4 uses the carry flag and codice_5 uses the overflow flag. Other conditional instructions look at combinations of several flags. Testing if certain bits in the FLAGS register are changeable allows determining what kind of processor is installed. For example, the alignment flag can only be changed on the 486 and above, so if it can be changed then the CPU is a 486 or higher. These methods of processor detection were not made obsolete by the CPUID instruction introduced with

neg: Processor supplementary capability supplementary capability" does not extend to Floating Point Units (FPUs) or Memory Management Units (MMUs) as these are considered to be fundamental core functionalities. Extensions to the core functionalities of the MMU and FPU may be considered CPU extensions however. The supplementary instructions feature has always been assumed to mean fixed sets of instructions that are not obligatory across all CPUs in a CPU family. Supplementary instructions will simply not be found on all processors within that family. A programmer who wishes to use a supplementary feature of a CPU is faced with a couple of choices. Supplemental instruction programming

neg: Process specification set of instructions outlining a business procedure that each elementary level business activity is expected to carry out. Process specifications are commonly included as an integral component of a requirements document in systems development. There are a variety of approaches that can be used to produce a process specification including No matter what approach is used, it must communicate to system development designers, implementers and support professionals, as well as be verifiable by the stakeholders/end users. Process specification Process specification is a generic term for the specification of a process. Its context is not unique to "business activity" but can

neg: CDC 6600 in ten cycles. However, the CPU could only execute a limited number of simple instructions. A typical CPU of the era had a complex instruction set, which included instructions to handle all the normal "housekeeping" tasks, such as memory access and input/output. Cray instead implemented these instructions in separate, simpler processors dedicated solely to these tasks, leaving the CPU with a much smaller instruction set. This was the first of what later came to be called reduced instruction set computer (RISC) design. By allowing the CPU, peripheral processors (PPs) and I/O to operate in parallel, the design considerably improved the

neg: Micro-operation Micro-operation In computer central processing units, micro-operations (also known as a micro-ops or μops) are detailed low-level instructions used in some designs to implement complex machine instructions (sometimes termed macro-instructions in this context). Usually, micro-operations perform basic operations on data stored in one or more registers, including transferring data between registers or between registers and external buses of the central processing unit (CPU), and performing arithmetic or logical operations on registers. In a typical fetch-decode-execute cycle, each step of a macro-instruction is decomposed during its execution so the CPU determines and steps through a series of micro-operations. The execution of

neg: Cycle stealing Apollo 11 landing to be aborted, but the design of the Apollo Guidance Computer allowed the landing to continue by dropping low-priority tasks. The IBM 1130's "cycle steal" is really DMA because the CPU clock is stopped during memory access. Several I/O controllers access RAM this way. They self-arbitrate via a fixed priority scheme. Most controllers deliberately pace RAM access to minimize impact on the system's ability to run instructions, but others, such as graphic video adapters, operate at higher speed and may slow down the system. The cycle-stealing concept of the 1130 permits the CPU program to start an

neg: Central processing unit a given cycle. Most of the difficulty in the design of a superscalar CPU architecture lies in creating an effective dispatcher. The dispatcher needs to be able to quickly and correctly determine whether instructions can be executed in parallel, as well as dispatch them in such a way as to keep as many execution units busy as possible. This requires that the instruction pipeline is filled as often as possible and gives rise to the need in superscalar architectures for significant amounts of CPU cache. It also makes hazard-avoiding techniques like branch prediction, speculative execution, register renaming, out-of-order execution and

neg: CDC 6600 we have lost our industry leadership position by letting someone else offer the world's most powerful computer." Cray's reply was sardonic: "It seems like Mr. Watson has answered his own question." Typical machines of the era used a single CPU to drive the entire system. A typical program would first load data into memory (often using pre-rolled library code), process it, and then write it back out. This required the CPUs to be fairly complex in order to handle the complete set of instructions they would be called on to perform. A complex CPU implied a large CPU, introducing signalling

neg: Avida that one organism executes, for example, twice as many instructions in the same time interval as another organism. The speed at which a virtual CPU runs is determined by a number of factors, but most importantly, by the "tasks" that the organism performs: logical computations that the organisms can carry out to reap extra CPU speed as bonus. Adami and Ofria, in collaboration with others, have used Avida to conduct research in digital evolution, and the scientific journals "Nature" and "Science" have published four of their papers. The 2003 paper "The Evolutionary Origin of Complex Features" describes the evolution of

neg: Transputer allowed it to be used as memory and included MMU-like functionality to handle all of this (termed the "PMI"). For more speed the T9000 cached the top 32 locations of the stack, instead of three as in earlier versions. The T9000 used a five-stage pipeline for even more speed. An interesting addition was the "grouper" which would collect instructions out of the cache and group them into larger packages of 4 bytes to feed the pipeline faster. Groups then completed in one cycle, as if they were single larger instructions working on a faster CPU. The link system was upgraded

neg: Hazard (computer architecture) Hazard (computer architecture) In the domain of central processing unit (CPU) design, hazards are problems with the instruction pipeline in CPU microarchitectures when the next instruction cannot execute in the following clock cycle, and can potentially lead to incorrect computation results. Three common types of hazards are data hazards, structural hazards, and control hazards (branching hazards). There are several methods used to deal with hazards, including pipeline stalls/pipeline bubbling, operand forwarding, and in the case of out-of-order execution, the scoreboarding method and the Tomasulo algorithm. Instructions in a pipelined processor are performed in several stages, so that at any given

neg: IBM zEC12 (microprocessor) nm CMOS silicon on insulator fabrication process, supporting speeds of 5.5 GHz, the highest clock speed CPU ever produced for commercial sale. The processor implements the CISC z/Architecture with a superscalar, out-of-order pipeline and some new instructions mainly related to transactional execution. The cores have numerous other enhancements such as better branch prediction, out of order execution and one dedicated co-processor for compression and cryptography. The instruction pipeline has 15 to 17 stages; the instruction queue can hold 40 instructions; and up to 90 instructions can be "in flight". It has six cores, each with a private 64 KB L1

neg: Half-carry flag Half-carry flag A half-carry flag (also known as an auxiliary flag or decimal adjust flag) is a condition flag bit in the status register of many CPU families, such as the Intel 8080, Zilog Z80, the x86, and the Atmel AVR series, among others. It indicates when a carry or borrow has been generated out of the least significant four bits of the accumulator register following the execution of an arithmetic instruction. It is primarily used in decimal (BCD) arithmetic instructions. Normally, a processor that utilizes binary arithmetic (which includes almost all modern CPUs) will add two 8-bit byte values

neg: Round-robin scheduling of the jobs, a process that produced large jobs would be favoured over other processes. Round-robin algorithm is a pre-emptive algorithm as the scheduler forces the process out of the CPU once the time quota expires. For example, if the time slot is 100 milliseconds, and "job1" takes a total time of 250 ms to complete, the round-robin scheduler will suspend the job after 100 ms and give other jobs their time on the CPU. Once the other jobs have had their equal share (100 ms each), "job1" will get another allocation of CPU time and the cycle will repeat.

neg: Bonnell (microarchitecture) Bonnell (microarchitecture) Bonnell is a CPU microarchitecture used by Intel Atom processors which can execute up to two instructions per cycle. Like many other x86 microprocessors, it translates x86 instructions (CISC instructions) into simpler internal operations (sometimes referred to as micro-ops, effectively RISC style instructions) prior to execution. The majority of instructions produce one micro-op when translated, with around 4% of instructions used in typical programs producing multiple micro-ops. The number of instructions that produce more than one micro-op is significantly fewer than the P6 and NetBurst microarchitectures. In the Bonnell microarchitecture, internal micro-ops can contain both a memory load

neg: CDC 6600 the 6600 exploited. Instead of trying to make the CPU handle all the tasks, the 6600 CPUs handled arithmetic and logic only. This resulted in a much smaller CPU that could operate at a higher clock speed. Combined with the faster switching speeds of the silicon transistors, the new CPU design easily outperformed everything then available. The new design ran at 10 MHz (100 ns cycle), about ten times faster than other machines on the market. In addition to the clock being faster, the simple processor executed instructions in fewer clock cycles; for instance, the CPU could complete a multiplication

neg: Intel ADX the rest of the CPU flags. Having two versions affecting different flags means that two chains of additions with carry can be calculated in parallel. AMD added support in their processors for these instructions starting with Ryzen. Intel ADX Intel ADX (Multi-Precision Add-Carry Instruction Extensions) is Intel's arbitrary-precision arithmetic extension to the x86 instruction set architecture (ISA). Intel ADX was first supported in the Broadwell microarchitecture. The instruction set extension contains just two new instructions, though codice_1 from BMI2 is also considered as a part of the large integer arithmetic support. Both instructions are more efficient variants of the existing

neg: System Idle Process the System Idle Process are also used to implement CPU power saving. The exact power saving scheme depends on the operating system version and on the hardware and firmware capabilities of the system in question. For instance, on x86 processors under Windows 2000, the idle thread will run a loop of halt instructions, which causes the CPU to turn off many internal components until an interrupt request arrives. Later versions of Windows implement more complex CPU power saving methods. On these systems the idle thread will call routines in the Hardware Abstraction Layer to reduce CPU clock speed or to

neg: System time handle such conversions may also deal with adjustments for timezones, daylight saving time (DST), leap seconds, and the user's locale settings. Library routines are also generally provided that convert calendar times into system times. Closely related to system time is "process time", which is a count of the total CPU time consumed by an executing process. It may be split into "user" and "system" CPU time, representing the time spent executing user code and system kernel code, respectively. Process times are a tally of CPU instructions or clock cycles and generally have no direct correlation to wall time. File systems

neg: Apollo PRISM Equipment Corporation's Alpha. In some respects, the VLIW design can be thought of as "super-RISCy", as it offloads the instruction selection process to the compiler as well. In the VLIW design, the compiler examines the code and selects instructions that are known to be "safe", and then packages them into longer instruction words. For instance, for a CPU with two functional units, like the PRISM, the compiler would find pairs of safe instructions and stuff them into a single larger word. Inside the CPU, the instructions are simply split apart again, and fed into the selected units. This design minimizes

neg: Joel McCormack computed register to the destination bus in a single microcycle. The cpu ran at three different clock speeds (using delay lines for a selectable clock); two bits in the microword selected the cycle time for that instruction. The clocks around 130, 150, and 175 nanoseconds. Newer parts from AMD would have allowed a faster 98 ns cycle for the fastest instructions, but they didn't come out with a correspondingly faster branch control unit. There was a separate prefetch/instruction formatting unit (again, using stoppable delay line clocks for synchronization...asynchronous logic allows for skewed timings). It had a 32-bit buffer and could

neg: CPU time CPU time CPU time (or process time) is the amount of time for which a central processing unit (CPU) was used for processing instructions of a computer program or operating system, as opposed to elapsed time, which includes for example, waiting for input/output (I/O) operations or entering low-power (idle) mode. The CPU time is measured in clock ticks or seconds. Often, it is useful to measure CPU time as a percentage of the CPU's capacity, which is called the CPU usage. CPU time and CPU usage have two main uses. The first use is to quantify the overall busyness of

neg: Motorola 68030 for the caches, where four longwords can be placed in the cache without further CPU intervention. Motorola used the process shrink to pack more hardware on the die; in this case it was the MMU, which mostly (but not completely) compatible with the external 68851. The integration of the MMU made it more cost-effective than the 68020 with an external MMU; it also allowed the 68030 to access memory one cycle faster than a 68020/68851 combo. However, the 68030 can switch between synchronous and asynchronous buses without a reset. The 68030 also lacks some of the 68020's instructions, but it

neg: IBM z196 fabrication process, supporting speeds of 5.2 GHz: at the time, the highest clock speed CPU ever produced for commercial sale. The processor implements the CISC z/Architecture with a new superscalar, out-of-order pipeline and 100 new instructions. The instruction pipeline has 15 to 17 stages; the instruction queue can hold 40 instructions; and up to 72 instructions can be "in flight". It has four cores, each with a private 64 KB L1 instruction cache, a private 128 KB L1 data cache and a private 1.5 MB L2 cache. In addition, there is a 24 MB shared L3 cache implemented in eDRAM

neg: Dynamips is emulating a router’s CPU instruction-by-instruction. it initially has no way of knowing when the virtual router’s CPU is idle so it dutifully executes all the instructions that make up IOS’s idle routines just as it would execute the instructions that perform “real” work. But once you have run through the “Idle-PC” process for a given IOS image, CPU utilization decreases drastically. Dynamips Dynamips is an emulator computer program that was written to emulate Cisco routers. It has been created by Christophe Fillot who started his work in August 2005. Dynamips runs on FreeBSD, Linux, Mac OS X or Windows

neg: Superscalar processor Superscalar processor A superscalar processor is a CPU that implements a form of parallelism called instruction-level parallelism within a single processor. In contrast to a scalar processor that can execute at most one single instruction per clock cycle, a superscalar processor can execute more than one instruction during a clock cycle by simultaneously dispatching multiple instructions to different execution units on the processor. It therefore allows for more throughput (the number of instructions that can be executed in a unit of time) than would otherwise be possible at a given clock rate. Each execution unit is not a separate processor

neg: Process (computing) Threads came somewhat later. However, with the advent of concepts such as time-sharing, computer networks, and multiple-CPU shared memory computers, the old "multiprogramming" gave way to true multitasking, multiprocessing and, later, multithreading. Process (computing) In computing, a process is the instance of a computer program that is being executed. It contains the program code and its activity. Depending on the operating system (OS), a process may be made up of multiple threads of execution that execute instructions concurrently. While a computer program is a passive collection of instructions, a process is the actual execution of those instructions. Several processes may

neg: Kindergarten readiness it will be for the child to effectively focus her attention. Another important aspect of learning involves the ability to discern what is relevant from what is not. In everyday conversation we are continuously picking out the important parts of what is being said in order to commit the relevant information to memory. This skill is particularly important for children to be able to learn and follow instructions in a classroom environment. When young children listen to someone speaking, such as instructions from a teacher, it is important for them to be able to pick out the important information so

neg: Reduced instruction set computer have a larger set of instructions than many CISC CPUs. Some RISC processors such as the PowerPC have instruction sets as large as the CISC IBM System/370, for example; conversely, the DEC PDP-8—clearly a CISC CPU because many of its instructions involve multiple memory accesses—has only 8 basic instructions and a few extended instructions. The term "reduced" in that phrase was intended to describe the fact that the amount of work any single instruction accomplishes is reduced—at most a single data memory cycle—compared to the "complex instructions" of CISC CPUs that may require dozens of data memory cycles in order

neg: Address generation unit 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 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

neg: Addressing mode other instructions—branch instructions—in order to make these sequential instructions run faster. Conditional branches load the PC with one of 2 possible results, depending on the condition—most CPU architectures use some other addressing mode for the "taken" branch, and sequential execution for the "not taken" branch. Many features in modern CPUs -- instruction prefetch and more complex pipelineing, out-of-order execution, etc. -- maintain the illusion that each instruction finishes before the next one begins, giving the same final results, even though that's not exactly what happens internally. Each "basic block" of such sequential instructions exhibits both temporal and spatial locality of

neg: Vortex86 a single 720-pin BGA-package. The CPU implements the i586 architecture, but the early versions Vortex86 original and Vortex86SX do not have a floating point unit (FPU). Any code that runs on an i486SX CPU without a 487 will run on Vortex86, as will any code that runs on i586 but does not use floating point instructions. Any i586 code will run on Vortex86DX and later. Some Linux kernels (by build-time option) emulate the FPU on any CPU that is missing one, so that even a program that uses floating point instructions, if it runs under Linux, works on any Vortex86

neg: Intel 8087 ASCII character ESC although in the higher order bits of a byte; similar instruction prefixes are also sometimes referred to as "escape codes". The instruction mnemonic assigned by Intel for these coprocessor instructions is "ESC". When the 8086 or 8088 CPU executed the ESC instruction, if the second byte (the ModR/M byte) specified a memory operand, the CPU would execute a bus cycle to read one word from the memory location specified in the instruction (using any 8086 addressing mode), but it would not store the read operand into any CPU register or perform any operation on it; the 8087

neg: Sum addressed decoder Sum addressed decoder In CPU design, the use of a Sum Addressed Decoder (SAD) or Sum Addressed Memory (SAM) Decoder is a method of reducing the latency of the CPU cache access. This is achieved by fusing the address generation sum operation with the decode operation in the cache SRAM. The L1 data cache should usually be in the most critical CPU resource, because few things improve instructions per cycle (IPC) as directly as a larger data cache, a larger data cache takes longer to access, and pipelining the data cache makes IPC worse. One way of reducing the latency

neg: Reversible process (thermodynamics) "reversible cycle", a cyclical reversible process, the system and its surroundings will be returned to their original states if one half cycle is followed by the other half cycle. Thermodynamic processes can be carried out in one of two ways: reversibly or irreversibly. Reversibility means the reaction operates continuously at quasiequilibrium. In an ideal thermodynamically reversible process, the energy from work performed by or on the system would be maximized, and that from heat would be zero. However, heat cannot fully be converted to work and will always be lost to some degree (to the surroundings). (This is true only

neg: R3000 other instruction set features—fixed instruction length and only three different types of instruction formats—greatly simplify instruction decoding and processing. To speed up processing even further the CPU employs a 5-stage instruction pipeline. The pipeline design allows the R3000 CPU to execute most instructions at a rate close to 1 instruction per cycle. The MIPS architecture supports up to four coprocessors. In addition to the CPU core, the R3000 microprocessor includes a Control Processor (CP), which contains a Translation Lookaside Buffer and a Memory Management Unit. The CP works as a coprocessor. Besides the CP, the R3000 can also support an

neg: Vector processor 1990s. Other CPU designs include some multiple instructions for vector processing on multiple (vectorised) data sets, typically known as MIMD (Multiple Instruction, Multiple Data) and realized with VLIW (Very Long Instruction Word). The Fujitsu FR-V VLIW/"vector processor" combines both technologies. Vector processing development began in the early 1960s at Westinghouse in their "Solomon" project. Solomon's goal was to dramatically increase math performance by using a large number of simple math co-processors under the control of a single master CPU. The CPU fed a single common instruction to all of the arithmetic logic units (ALUs), one per cycle, but with a

neg: Half-carry flag 39 and 48 produces 81. This result does not have a non-decimal low nibble, but it does cause a carry out of the least significant digit (lower four bits) into the most significant digit (upper four bits). This is indicated by the CPU setting the half-carry flag. This value must also be corrected, by adding 06 to 81 to produce a corrected BCD result of 87. Finally, if an addition results in a non-decimal high digit, then 60 must be added to the value to produce the correct BCD result. For example, adding 72 and 73 produces E5. Since the

neg: Sum addressed decoder No.: 08/402,322, Filed: March 10, 1995 Sum addressed decoder In CPU design, the use of a Sum Addressed Decoder (SAD) or Sum Addressed Memory (SAM) Decoder is a method of reducing the latency of the CPU cache access. This is achieved by fusing the address generation sum operation with the decode operation in the cache SRAM. The L1 data cache should usually be in the most critical CPU resource, because few things improve instructions per cycle (IPC) as directly as a larger data cache, a larger data cache takes longer to access, and pipelining the data cache makes IPC worse.

neg: PowerPC 600 which never reached mass production. Its main feature was to incorporate an x86 core on die, thus making the processor able to natively process both PowerPC and x86 instructions. An operating system running on PowerPC 615 could either chose to execute 32-bit or 64-bit PowerPC instructions, 32-bit x86 instructions or a mix of three. Mixing instructions would involve a context switch in the CPU with a small overhead. The only operating systems that supported the 615 were Minix and a special development version of OS/2. It was 330 mm² large and manufactured by IBM on a 0.35 µm process. It

neg: CPU time or other resources. Example: A software application executed on a hexa-core processor creates three Unix processes for fulfilling the user requirement. Each of these three processes creates two threads, enumerating a total of 6 working threads. Computation is distributed evenly on the 6 independent threads. If no wait for resources is involved, total CPU time is expected to be six times the elapsed real time. CPU time CPU time (or process time) is the amount of time for which a central processing unit (CPU) was used for processing instructions of a computer program or operating system, as opposed to elapsed

neg: Vector processor and getting the data out of the memory takes some time, during which the CPU traditionally would sit idle waiting for the requested data to show up. As CPU speeds have increased, this "memory latency" has historically become a large impediment to performance; see Memory wall. In order to reduce the amount of time consumed by these steps, most modern CPUs use a technique known as instruction pipelining in which the instructions pass through several sub-units in turn. The first sub-unit reads the address and decodes it, the next "fetches" the values at those addresses, and the next does the

neg: Computer data storage Historically, "memory" has been called "core memory", "main memory", "real storage" or "internal memory". Meanwhile, non-volatile storage devices have been referred to as "secondary storage", "external memory" or "auxiliary/peripheral storage". "Primary storage" (also known as "main memory" or "internal memory"), often referred to simply as "memory", is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in uniform manner. Historically, early computers used delay lines, Williams tubes, or rotating magnetic drums as primary storage. By 1954, those unreliable methods were

neg: Software computer to carry out an operation—moving data, carrying out a computation, or altering the control flow of instructions. Data movement is typically from one place in memory to another. Sometimes it involves moving data between memory and registers which enable high-speed data access in the CPU. Moving data, especially large amounts of it, can be costly. So, this is sometimes avoided by using "pointers" to data instead. Computations include simple operations such as incrementing the value of a variable data element. More complex computations may involve many operations and data elements together. Software quality is very important, especially for commercial

neg: XC2000 decoding instructions, to supply, perform operations and store calculated result on the operands for the arithmetic logic unit (ALU) and the MAC unit. As the CPU is the main engine of the XC2000 microcontroller, it is also affected by certain actions of the peripheral subsystem. Because a five-stage processing pipeline (plus two-stage fetch pipeline) is implemented in the XC2000, up to five instructions can be processed in parallel. Most instructions of the XC2000 are executed in one single clock cycle due to this parallelism. There are "Easy Kits" for evaluation of the controller features and "Application Kits" as quick start

neg: Illegal opcode long. A danger associated with the use of illegal instructions was that, given the fact that the manufacturer does not guarantee their existence and function, they might disappear or behave differently with any change of the CPU internals or any new revision of the CPU, rendering programs that use them incompatible with the newer revisions. For example, a number of older Apple II games do not work correctly on the newer Apple IIc, because the latter uses a newer CPU revision 65C02 that does away with illegal opcodes. More recent CPUs, such as the 80186, 80286, 68000 and its descendants

neg: Bonnell (microarchitecture) Clover Trail tablet platform. In December 2012 Intel launched the 64-bit Centerton family of Atom CPUs, designed specifically for use in Bordenville platform servers. Based on the 32 nm Saltwell architecture, Centerton adds features previously unavailable in most Atom processors, such as Intel VT virtualization technology, and support for ECC memory. Briarwood is an Atom SoC that is designed for a server platform. Bonnell (microarchitecture) Bonnell is a CPU microarchitecture used by Intel Atom processors which can execute up to two instructions per cycle. Like many other x86 microprocessors, it translates x86 instructions (CISC instructions) into simpler internal operations (sometimes

neg: Microarchitecture repeated continuously until the power is turned off. Complicating this simple-looking series of steps is the fact that the memory hierarchy, which includes caching, main memory and non-volatile storage like hard disks (where the program instructions and data reside), has always been slower than the processor itself. Step (2) often introduces a lengthy (in CPU terms) delay while the data arrives over the computer bus. A considerable amount of research has been put into designs that avoid these delays as much as possible. Over the years, a central goal was to execute more instructions in parallel, thus increasing the effective

neg: Reduced instruction set computer for a reasonably sized constant in a 32-bit instruction word. Since many real-world programs spend most of their time executing simple operations, some researchers decided to focus on making those operations as fast as possible. The clock rate of a CPU is limited by the time it takes to execute the slowest "sub-operation" of any instruction; decreasing that cycle-time often accelerates the execution of other instructions. The focus on "reduced instructions" led to the resulting machine being called a "reduced instruction set computer" (RISC). The goal was to make instructions so simple that they could "easily" be pipelined, in order

neg: XE166 family the XE166 microcontroller family is principally fetching and decoding instructions, to supply, perform operations and store calculated result on the operands for the arithmetic logic unit (ALU) and the MAC unit. As the CPU is the main engine of the XE166 microcontroller, it is also affected by certain actions of the peripheral subsystem. Because a five-stage processing pipeline (plus two-stage fetch pipeline) is implemented in the XE166, up to five instructions can be processed in parallel. Most instructions of the XE166 are executed in a single clock cycle due to this parallelism. There are "Easy Kits" for evaluation of the

neg: XC 2000 family and decoding instructions, to supply, perform operations and store calculated result on the operands for the arithmetic logic unit (ALU) and the MAC unit. As the CPU is the main engine of the XC2000 microcontroller, it is also affected by certain actions of the peripheral subsystem. Because a five-stage processing pipeline (plus two-stage fetch pipeline) is implemented in the XC2000, up to five instructions can be processed in parallel. Most instructions of the XC2000 are executed in one single clock cycle due to this parallelism. There are "Easy Kits" for evaluation of the controller features and "Application Kits" as quick

neg: Streaming SIMD Extensions means that the OS must know how to use the codice_8 and codice_9 instructions, which is the extended pair of instructions which can save all x86 and SSE register states all at once. This support was quickly added to all major IA-32 operating systems. The first CPU to support SSE, the Pentium III, shared execution resources between SSE and the floating point unit (FPU). While a compiled application can interleave FPU and SSE instructions side-by-side, the Pentium III will not issue an FPU and an SSE instruction in the same clock cycle. This limitation reduces the effectiveness of pipelining, but

neg: Apollo Guidance Computer data in the G register was written back to memory. The AGC memory cycle occurred continuously during AGC operation. Instructions needing memory data had to access it during timing pulses 7-10. If the AGC changed the memory word in the G register, the changed word was written back to memory after timing pulse 10. In this way, data words cycled continuously from memory to the G register and then back again to memory. The lower 15 bits of each memory word held AGC instructions or data, with each word being protected by a 16th odd parity bit. This bit was

neg: History of general-purpose CPUs the operands for the next instruction while calculating the result of the current one. Modern CPUs may use over a dozen such stages. (Pipelining was originally developed in the late 1950s by International Business Machines (IBM) on their 7030 (Stretch) mainframe computer.) Minimal instruction set computers (MISC) can execute instructions in one cycle with no need for pipelining. A similar idea, introduced only a few years later, was to execute multiple instructions in parallel on separate arithmetic logic units (ALUs). Instead of operating on only one instruction at a time, the CPU will look for several similar instructions that do

neg: Object language have gone to great lengths to simplify the programmer's task. For example, a high level programming language may allow a programmer to assign a value to a variable without specifying a memory location or a CPU instruction. In this context, the high level programming language is the "source language", which is then translated by a compiler into object code that the CPU can read directly. This object code is the "object language", and varies depending on what CPU is being given the instructions. "Object language" in this context means something akin to "the object of what the programmer is trying

neg: Firmware implemented the computer's instruction set, and that could be reloaded to specialize or modify the instructions that the central processing unit (CPU) could execute. As originally used, firmware contrasted with hardware (the CPU itself) and software (normal instructions executing on a CPU). It was not composed of CPU machine instructions, but of lower-level microcode involved in the implementation of machine instructions. It existed on the boundary between hardware and software; thus the name "firmware". Over time, popular usage extended the word "firmware" to denote any computer program that is tightly linked to hardware, including processor machine instructions for BIOS, bootstrap

neg: XCore Architecture (r16 = pc = program counter, r17 = sr = status register), they are dedicated to exception and interrupt handling. The status register contains various mode bits, but the processor does "not" have the standard ALU result flags like carry, zero, negative or overflow. Add and subtract with carry instructions exist, but specify five operand registers: two inputs and input carry, and one output and output carry. Most instructions are 16-bit while a few have 32-bit encoding. Instructions can use between zero and six operands. Most common arithmetic operations (such as ADD, SUB, MULT) are three-operand instructions based on a

neg: Intel 8087 would observe the bus and decode the instruction stream in sync with the 8086, recognizing the coprocessor instructions meant for itself. For an 8087 instruction with a memory operand, if the instruction called for the operand to be read, the 8087 would take the word of data read by the main CPU from the data bus. If the operand to be read was longer than one word, the 8087 would also copy the address from the address bus; then, after completion of the data read cycle driven by the CPU, the 8087 would immediately use DMA to take control of

neg: POWER3 which allowed more instructions to be executed out of order, improving performance. Execution begins in stage four. The instruction queues dispatch up to eight instructions to the execution units. Integer instructions are executed in three integer execution units (termed "fixed-point units" by IBM). Two of the units are identical and execute all integer instructions except for multiply and divide. All instructions executed by them have a one-cycle latency. The third unit executes multiply and divide instructions. These instructions are not pipelined and have multi-cycle latencies. 64-bit multiply has a nine-cycle latency and 64-bit divide has a 37-cycle latency. Floating-point instructions

neg: Intel 8088 a shifted segment register to the offset address, but the offset EA itself is always calculated entirely in the main ALU. Furthermore, the loose coupling of the EU and BIU (bus unit) inserts communication overhead between the units, and the four-clock period bus transfer cycle is not particularly streamlined. Contrast this with the two-clock period bus cycle of the 6502 CPU and the 80286's three-clock period bus cycle with pipelining down to two cycles for most transfers. Most 8088 instructions that can operate on either registers or memory, including common ALU and data-movement operations, are at least four times slower

neg: Analytical Engine regularized grid layout. Like the central processing unit (CPU) in a modern computer, the mill would rely upon its own internal procedures, to be stored in the form of pegs inserted into rotating drums called "barrels", to carry out some of the more complex instructions the user's program might specify. The programming language to be employed by users was akin to modern day assembly languages. Loops and conditional branching were possible, and so the language as conceived would have been Turing-complete as later defined by Alan Turing. Three different types of punch cards were used: one for arithmetical operations, one

neg: Sun the poloidal field is at its maximum strength. With the rise of the next 11-year sunspot cycle, differential rotation shifts magnetic energy back from the poloidal to the toroidal field, but with a polarity that is opposite to the previous cycle. The process carries on continuously, and in an idealized, simplified scenario, each 11-year sunspot cycle corresponds to a change, then, in the overall polarity of the Sun's large-scale magnetic field. The solar magnetic field extends well beyond the Sun itself. The electrically conducting solar wind plasma carries the Sun's magnetic field into space, forming what is called the interplanetary

neg: AMD K9 AMD K9 The AMD K9 represents a microarchitecture by AMD designed to replace the K8 processors, featuring dual-core processing. K9 appears originally to have been an ambitious 8 issue per clock cycle core redesign of the K7 or the K8 processor core. At one point, K9 was the "Greyhound" project at AMD, and was worked on by the K7 design team beginning in early 2001, with tape-out revision A0 scheduled for 2003. The L1 instruction cache was said to hold decoded instructions, essentially the same as Intel's trace cache. The existence of a massively parallel CPU design concept for heavily

neg: Escalation archetype than Amy. This is noted by Cecile and she does what must be done - starts working more than anyone else. But there is also Danielle whose ambitions are not even slightly smaller, she wants to be the most famous celebrity and so she starts working even harder than anyone else. As Amy notices her effort is not sufficient, she does what is obvious - starts to work more than she was. Now this cycle could repeat continuously until Amy, Betty, Cecile or Danielle dies of overwork. In the meanwhile some of them could start taking drugs with the presumption

neg: Process Explorer can be used to track down what is holding a file open and preventing its use by another program. As another example, it can show the command lines used to start a program, allowing otherwise identical processes to be distinguished. Like Task Manager, it can show a process that is maxing out the CPU, but unlike Task Manager it can show which thread (with the callstack) is using the CPU – information that is not even available under a debugger. Process Explorer began in the early Sysinternals days as two separate utilities, HandleEx and DLLView, which were merged in 2001.

neg: Central processing unit parts of a CPU and provides various counters accessible to software; an example is Intel's "Performance Counter Monitor" technology. Central processing unit A central processing unit (CPU) is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logic, controlling, and input/output (I/O) operations specified by the instructions. The computer industry has used the term "central processing unit" at least since the early 1960s. Traditionally, the term "CPU" refers to a processor, more specifically to its processing unit and control unit (CU), distinguishing these core elements of a computer from