A central processing unit (CPU), also called a central processor, main processor, or just processor, is the most important processor in a given computer. Its electronic circuitry executes instructions of a computer program, such as arithmetic, logic, controlling, and input/output (I/O) operations. This role contrasts with that of external components, such as main memory and I/O circuitry, and specialized coprocessors such as graphics processing units (GPUs).
The 8086 is a 16-bit microprocessor chip designed by Intel between early 1976 and June 8, 1978, when it was released. The Intel 8088, released July 1, 1979, is a slightly modified chip with an external 8-bit data bus, and is notable as the processor used in the original IBM PC design.
The Intel 8088 microprocessor is a variant of the Intel 8086. Introduced on June 1, 1979, the 8088 has an eight-bit external data bus instead of the 16-bit bus of the 8086. The 16-bit registers and the one megabyte address range are unchanged, however. In fact, according to the Intel documentation, the 8086 and 8088 have the same execution unit (EU)—only the bus interface unit (BIU) is different. The 8088 was used in the original IBM PC and in IBM PC compatible clones.
In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. A device or program that executes instructions described by that ISA, such as a central processing unit (CPU), is called an implementation of that ISA.
The Harvard architecture is a computer architecture with separate storage and signal pathways for instructions and data. It is often contrasted with the von Neumann architecture, where program instructions and data share the same memory and pathways. This architecture is often used in real-time processing or low-power applications.
In computer engineering, instruction pipelining is a technique for implementing instruction-level parallelism within a single processor. Pipelining attempts to keep every part of the processor busy with some instruction by dividing incoming instructions into a series of sequential steps performed by different processor units with different parts of instructions processed in parallel.
Speculative execution is an optimization technique where a computer system performs some task that may not be needed. Work is done before it is known whether it is actually needed, so as to prevent a delay that would have to be incurred by doing the work after it is known that it is needed. If it turns out the work was not needed after all, most changes made by the work are reverted and the results are ignored.
Fetching the instruction opcodes from program memory well in advance is known as prefetching and it is served by using a prefetch input queue (PIQ). The pre-fetched instructions are stored in a queue. The fetching of opcodes well in advance, prior to their need for execution, increases the overall efficiency of the processor boosting its speed. The processor no longer has to wait for the memory access operations for the subsequent instruction opcode to complete. This architecture was prominently used in the Intel 8086 microprocessor.
In computer science, computer engineering and programming language implementations, a stack machine is a computer processor or a virtual machine in which the primary interaction is moving short-lived temporary values to and from a push down stack. In the case of a hardware processor, a hardware stack is used. The use of a stack significantly reduces the required number of processor registers. Stack machines extend push-down automata with additional load/store operations or multiple stacks and hence are Turing-complete.
The instruction cycle is the cycle that the central processing unit (CPU) follows from boot-up until the computer has shut down in order to process instructions. It is composed of three main stages: the fetch stage, the decode stage, and the execute stage.
Explicitly parallel instruction computing (EPIC) is a term coined in 1997 by the HP–Intel alliance to describe a computing paradigm that researchers had been investigating since the early 1980s. This paradigm is also called Independence architectures. It was the basis for Intel and HP development of the Intel Itanium architecture, and HP later asserted that "EPIC" was merely an old term for the Itanium architecture. EPIC permits microprocessors to execute software instructions in parallel by using the compiler, rather than complex on-die circuitry, to control parallel instruction execution. This was intended to allow simple performance scaling without resorting to higher clock frequencies.
A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average cost to access data from the main memory. A cache is a smaller, faster memory, located closer to a processor core, which stores copies of the data from frequently used main memory locations. Most CPUs have a hierarchy of multiple cache levels, with different instruction-specific and data-specific caches at level 1. The cache memory is typically implemented with static random-access memory (SRAM), in modern CPUs by far the largest part of them by chip area, but SRAM is not always used for all levels, or even any level, sometimes some latter or all levels are implemented with eDRAM.
The Intel 8087, announced in 1980, was the first floating-point coprocessor for the 8086 line of microprocessors. The purpose of the chip was to speed up floating-point arithmetic operations, such as addition, subtraction, multiplication, division, and square root. It also computes transcendental functions such as exponential, logarithmic or trigonometric calculations. The performance enhancements were from approximately 20% to over 500%, depending on the specific application. The 8087 could perform about 50,000 FLOPS using around 2.4 watts.
In electronics, computer science and computer engineering, microarchitecture, also called computer organization and sometimes abbreviated as μarch or uarch, is the way a given instruction set architecture (ISA) is implemented in a particular processor. A given ISA may be implemented with different microarchitectures; implementations may vary due to different goals of a given design or due to shifts in technology.
The Prefetcher is a component of Microsoft Windows which was introduced in Windows XP. It is a component of the Memory Manager that can speed up the Windows boot process and shorten the amount of time it takes to start up programs. It accomplishes this by caching files that are needed by an application to RAM as the application is launched, thus consolidating disk reads and reducing disk seeks. This feature was covered by US patent 6,633,968.
Joel McCormack is an American computer scientist who designed the NCR Corporation version of the p-code machine, which is a kind of stack machine popular in the 1970s as the preferred way to implement new computing architectures and languages such as Pascal and BCPL. The NCR design shares no common architecture with the Pascal MicroEngine designed by Western Digital but both were meant to execute the UCSD p-System.[1,2]
A modified Harvard architecture is a variation of the Harvard computer architecture that, unlike the pure Harvard architecture, allows memory that contains instructions to be accessed as data. Most modern computers that are documented as Harvard architecture are, in fact, modified Harvard architecture.
This glossary of computer hardware terms is a list of definitions of terms and concepts related to computer hardware, i.e. the physical and structural components of computers, architectural issues, and peripheral devices.
In computing, a cache control instruction is a hint embedded in the instruction stream of a processor intended to improve the performance of hardware caches, using foreknowledge of the memory access pattern supplied by the programmer or compiler. They may reduce cache pollution, reduce bandwidth requirement, bypass latencies, by providing better control over the working set. Most cache control instructions do not affect the semantics of a program, although some can.
Cache prefetching is a technique used by computer processors to boost execution performance by fetching instructions or data from their original storage in slower memory to a faster local memory before it is actually needed. Most modern computer processors have fast and local cache memory in which prefetched data is held until it is required. The source for the prefetch operation is usually main memory. Because of their design, accessing cache memories is typically much faster than accessing main memory, so prefetching data and then accessing it from caches is usually many orders of magnitude faster than accessing it directly from main memory. Prefetching can be done with non-blocking cache control instructions.
