X86x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant. The 8086 was introduced in 1978 as a fully 16-bit extension of Intel's 8-bit 8080 microprocessor, with memory segmentation as a solution for addressing more memory than can be covered by a plain 16-bit address.
Pentium ProThe Pentium Pro is a sixth-generation x86 microprocessor developed and manufactured by Intel and introduced on November 1, 1995. It introduced the P6 microarchitecture (sometimes termed i686) and was originally intended to replace the original Pentium in a full range of applications. While the Pentium and Pentium MMX had 3.1 and 4.5 million transistors, respectively, the Pentium Pro contained 5.5 million transistors.
Pentium (original)The Pentium (also referred to as P5, its microarchitecture, or i586) is a fifth generation, 32-bit x86 microprocessor that was introduced by Intel on March 22, 1993, as the very first CPU in the Pentium brand. It was instruction set compatible with the 80486 but was a new and very different microarchitecture design from previous iterations. The P5 Pentium was the first superscalar x86 microarchitecture and the world's first superscalar microprocessor to be in mass productionmeaning it generally executes at least 2 instructions per clock mainly because of a design-first dual integer pipeline design previously thought impossible to implement on a CISC microarchitecture.
MicroprocessorA microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, and control circuitry required to perform the functions of a computer's central processing unit (CPU). The IC is capable of interpreting and executing program instructions and performing arithmetic operations.
PentiumPentium is a series of x86 architecture-compatible microprocessors produced by Intel. The original Pentium was first released on March 22, 1993. Pentium-branded processors released from 2009 to 2022 are considered entry-level products that Intel rates as "two stars", meaning that they are above the low-end Atom and Celeron series, but below the faster Intel Core lineup and workstation/server Xeon series. These later Pentium processors have little more than their name in common with earlier Pentiums, which were Intel's flagship processor for over a decade until the introduction of the Intel Core line in 2006.
Superscalar processorA 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, which 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 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.
CeleronCeleron is a series of low-end IA-32 and x86-64 computer microprocessor models targeted at low-cost personal computers, manufactured by Intel. The first Celeron-branded CPU was introduced in April 15, 1998, and was based on the Pentium II. Celeron-branded processors released from 2009 to 2022 are compatible with IA-32 software. They typically offer less performance per clock speed compared to flagship Intel CPU lines, such as the Pentium or Core brands. They often have less cache or intentionally disabled advanced features, with variable impact on performance.
Cyrix 6x86The Cyrix 6x86 is a line of sixth-generation, 32-bit x86 microprocessors designed and released by Cyrix in 1995. Cyrix, being a fabless company, had the chips manufactured by IBM and SGS-Thomson. The 6x86 was made as a direct competitor to Intel's Pentium microprocessor line, and was pin compatible. During the 6x86's development, the majority of applications (office software as well as games) performed almost entirely integer operations. The designers foresaw that future applications would most likely maintain this instruction focus.
Out-of-order executionIn computer engineering, out-of-order execution (or more formally dynamic execution) is a paradigm used in most high-performance central processing units to make use of instruction cycles that would otherwise be wasted. In this paradigm, a processor executes instructions in an order governed by the availability of input data and execution units, rather than by their original order in a program. In doing so, the processor can avoid being idle while waiting for the preceding instruction to complete and can, in the meantime, process the next instructions that are able to run immediately and independently.
CyrixCyrix Corporation was a microprocessor developer that was founded in 1988 in Richardson, Texas, as a specialist supplier of floating point units for 286 and 386 microprocessors. The company was founded by Tom Brightman and Jerry Rogers. In 1992, Cyrix introduced its own i386 compatible processors, the 486SLC and 486DLC. These were higher performance than the Intel parts, but lower price. They were primarily marketed to users looking to upgrade existing machines.
Register renamingIn computer architecture, register renaming is a technique that abstracts logical registers from physical registers. Every logical register has a set of physical registers associated with it. When a machine language instruction refers to a particular logical register, the processor transposes this name to one specific physical register on the fly. The physical registers are opaque and cannot be referenced directly but only via the canonical names.
AthlonAthlon is the brand name applied to a series of x86-compatible microprocessors designed and manufactured by AMD. The original Athlon (now called Athlon Classic) was the first seventh-generation x86 processor and the first desktop processor to reach speeds of one gigahertz (GHz). It made its debut as AMD's high-end processor brand on June 23, 1999. Over the years AMD has used the Athlon name with the 64-bit Athlon 64 architecture, the Athlon II, and Accelerated Processing Unit (APU) chips targeting the Socket AM1 desktop SoC architecture, and Socket AM4 Zen microarchitecture.
Pentium IIThe Pentium II brand refers to Intel's sixth-generation microarchitecture ("P6") and x86-compatible microprocessors introduced on May 7, 1997. Containing 7.5 million transistors (27.4 million in the case of the mobile Dixon with 256 KB L2 cache), the Pentium II featured an improved version of the first P6-generation core of the Pentium Pro, which contained 5.5 million transistors. However, its L2 cache subsystem was a downgrade when compared to the Pentium Pros. It is a single-core microprocessor.
Front-side busThe front-side bus (FSB) is a computer communication interface (bus) that was often used in Intel-chip-based computers during the 1990s and 2000s. The EV6 bus served the same function for competing AMD CPUs. Both typically carry data between the central processing unit (CPU) and a memory controller hub, known as the northbridge. Depending on the implementation, some computers may also have a back-side bus that connects the CPU to the cache. This bus and the cache connected to it are faster than accessing the system memory (or RAM) via the front-side bus.
NexGenNexGen, Inc. was a private semiconductor company based in Milpitas, California, that designed x86 microprocessors until it was purchased by AMD in 1996. NexGen was a fabless design house that designed its chips but relied on other companies for production. NexGen's chips were produced by IBM's Microelectronics division in Burlington, Vermont alongside PowerPC and DRAM parts. The company was best known for the unique implementation of the x86 architecture in its processors.
AMD K5The K5 is AMD's first x86 processor to be developed entirely in-house. Introduced in March 1996, its primary competition was Intel's Pentium microprocessor. The K5 was an ambitious design, closer to a Pentium Pro than a Pentium regarding technical solutions and internal architecture. However, the final product was closer to the Pentium regarding performance, although faster clock-for-clock compared to the Pentium. The K5 was based upon an internal highly parallel RISC processor architecture with an x86 decoding front-end.
