AB
DesignerIntel, AMD
Bits16-bit, 32-bit and 64-bit
Introduced1978 (16-bit), 1985 (32-bit), 2003 (64-bit)
DesignCISC
TypeRegister–memory
EncodingVariable (1 to 15 bytes)
BranchingCondition code
EndiannessLittle
Page size8086–i286: 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, SSE4.1, SSE4.2, AES-NI, CLMUL, SM3, SM4, RDRAND, SHA, MPX, SME, SGX, XOP, F16C, ADX, BMI, FMA, AVX, AVX2, AVX-VNNI, AVX-IFMA, AVX512, AVX10, AMX, VT-x, VT-d, AMD-V, AMD-Vi, TSX, ASF, TXT, APX
OpenMixed
Registers
General-purpose• 16-bit: 8 GPRs, including BP and SP
• 32-bit: 8 GPRs, including EBP and ESP
• 64-bit: 16 GPRs, including RBP and RSP
• 32 GPRs, If CPU supports APX
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

x86

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