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The 8086 [3] (also called iAPX 86) [4] 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, [5] is a slightly modified chip with an external 8-bit data bus (allowing the use of cheaper and fewer supporting ICs), [note 1] and is notable as the processor used in the original IBM PC design.
Used in Pentium 4, Pentium D, and some Xeon microprocessors. Very long pipeline. The Prescott was a major architectural revision. Later revisions were the first to feature Intel's x86-64 architecture, enhanced branch prediction and trace cache, and eventually support was added for the NX (No eXecute) bit to implement executable-space protection.
x86 (also known as 80x86 [3] or the 8086 family [4]) is a family of complex instruction set computer (CISC) instruction set architectures [a] initially developed by Intel, based on the 8086 microprocessor and its 8-bit-external-bus variant, the 8088.
Below is the full 8086/8088 instruction set of Intel (81 instructions total). [2] These instructions are also available in 32-bit mode, in which they operate on 32-bit registers (eax, ebx, etc.) and values instead of their 16-bit (ax, bx, etc.) counterparts.
In marketing, iAPX (Intel Advanced Performance Architecture [1]) was a short lived designation used for several Intel microprocessors, including some 8086 family processors. [2] Not being a simple initialism seems to have confused even Intel's technical writers as can be seen in their iAPX-88 Book where the asterisked expansion shows iAPX to ...
Before the 386 the only way to switch from protected mode back to real mode was to reset the processor; after a reset it always starts up in real mode to be compatible with earlier x86 CPUs back to the 8086. Resetting the processor does not clear the system's RAM, so this, while awkward and inefficient, is actually feasible.
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.
With AMD's introduction of a 64-bit architecture backwards-compatible with x86, x86-64 (also called AMD64), in September 2003, followed by Intel's near fully compatible 64-bit extensions (first called IA-32e or EM64T, later renamed Intel 64), the 64-bit desktop era began. Both versions can run 32-bit legacy applications without any performance ...