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Bound copy, from the 1980s, of the MIL-STD-1750A specification document. The 1750A supports 2 16 16-bit words of memory for the core standard. The standard defines an optional memory management unit that allows 2 20 16-bit words of memory using 512 page mapping registers (in the I/O space), defining separate instruction and data spaces, and keyed memory access control.
The x86 instruction set has several times been extended with SIMD (Single instruction, multiple data) instruction set extensions.These extensions, starting from the MMX instruction set extension introduced with Pentium MMX in 1997, typically define sets of wide registers and instructions that subdivide these registers into fixed-size lanes and perform a computation for each lane in parallel.
The AVX instruction set is the first instruction set extension to use the VEX coding scheme. The AVX instruction set uses VEX prefix only for instructions using the SIMD XMM registers. However, the VEX coding scheme has been used for other instruction types as well in subsequent expansions of the instruction set. For example:
While what these instructions do is similar to bit level gather-scatter SIMD instructions, PDEP and PEXT instructions (like the rest of the BMI instruction sets) operate on general-purpose registers. [12] The instructions are available in 32-bit and 64-bit versions. An example using arbitrary source and selector in 32-bit mode is:
Pentium II processor with MMX technology. MMX defines eight processor registers, named MM0 through MM7, and operations that operate on them.Each register is 64 bits wide and can be used to hold either 64-bit integers, or multiple smaller integers in a "packed" format: one instruction can then be applied to two 32-bit integers, four 16-bit integers, or eight 8-bit integers at once.
The XSAVE instruction set extensions are designed to save/restore CPU extended state (typically for the purpose of context switching) in a manner that can be extended to cover new instruction set extensions without the OS context-switching code needing to understand the specifics of the new extensions.
The primary defining characteristic of AMD64 is the availability of 64-bit general-purpose processor registers (for example, rax), 64-bit integer arithmetic and logical operations, and 64-bit virtual addresses. [16] The designers took the opportunity to make other improvements as well. Notable changes in the 64-bit extensions include:
Base instruction 0xFE 0x02 cgt: Push 1 (of type int32) if value1 greater than value2, else push 0. Base instruction 0xFE 0x03 cgt.un: Push 1 (of type int32) if value1 greater than value2, unsigned or unordered, else push 0. Base instruction 0xC3 ckfinite: Throw ArithmeticException if value is not a finite number. Base instruction 0xFE 0x04 clt ...