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Family of instruction set architectures / From Wikipedia, the free encyclopedia

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x86 (also known as 80x86[2] or the 8086 family[3]) is a family of complex instruction set computer (CISC) instruction set architectures[lower-alpha 1] 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. The term "x86" came into being because the names of several successors to Intel's 8086 processor end in "86", including the 80186, 80286, 80386 and 80486 processors.

Quick facts: Designer, Bits, Introduced, Design, Type...
DesignerIntel, AMD
Bits16-bit, 32-bit and 64-bit
Introduced1978 (16-bit), 1985 (32-bit), 2003 (64-bit)
EncodingVariable (1 to 15 bytes)
BranchingCondition code
Page size8086i286: None
i386, i486: 4 KB pages
P5 Pentium: added 4 MB pages
(Legacy PAE: 4 KB→2 MB)
x86-64: added 1 GB pages
Extensionsx87, IA-32, x86-64, MMX, 3DNow!, SSE, MCA, ACPI, SSE2, NX bit, SMT, SSE3, SSSE3, SSE4, SSE4.2, AES-NI, CLMUL, RDRAND, SHA, MPX, SME, SGX, XOP, F16C, ADX, BMI, FMA, AVX, AVX2, AVX-VNNI, AVX512, VT-x, VT-d, AMD-V, AMD-Vi, TSX, ASF, TXT
OpenPartly. For some advanced features, x86 may require license from Intel; x86-64 may require an additional license from AMD. The Pentium Pro processor (and NetBurst) has been on the market for more than 21 years[1] and so cannot be subject to patent claims. The i686 subset of the x86 architecture is therefore fully open.
General purpose
  • 16-bit: 6 semi-dedicated registers, BP and SP are not general-purpose
  • 32-bit: 8 GPRs, including EBP and ESP
  • 64-bit: 16 GPRs, including RBP and RSP
Floating point
  • 16-bit: optional separate x87 FPU
  • 32-bit: optional separate or integrated x87 FPU, integrated SSE units in later processors
  • 64-bit: integrated x87 and SSE2 units, later implementations extended to AVX2 and AVX512
The x86 architectures were based on the Intel 8086 microprocessor chip, initially released in 1978.
Intel Core 2 Duo, an example of an x86-compatible, 64-bit multicore processor
AMD Athlon (early version), a technically different but fully compatible x86 implementation

The term is not synonymous with IBM PC compatibility, as this implies a multitude of other computer hardware. Embedded systems and general-purpose computers used x86 chips before the PC-compatible market started,[lower-alpha 2] some of them before the IBM PC (1981) debut.

As of June 2022, most desktop and laptop computers sold are based on the x86 architecture family,[4] while mobile categories such as smartphones or tablets are dominated by ARM. At the high end, x86 continues to dominate computation-intensive workstation and cloud computing segments.[5] The fastest supercomputer in the TOP500 list for June 2022 was the first exascale system, Frontier,[6] built using AMD Epyc CPUs based on the x86 ISA; it broke the 1 exaFLOPS barrier in May 2022.[7]