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An address decoder is a particular use of a binary decoder circuit known as a "demultiplexer" or "demux" (the 74154 is commonly called a "4-to-16 demultiplexer"), which has many other uses besides address decoding. Address decoders are fundamental building blocks for systems that use buses.
In a computer using virtual memory, accessing the location corresponding to a memory address may involve many levels. In computing, a memory address is a reference to a specific memory location in memory used by both software and hardware. [1] These addresses are fixed-length sequences of digits, typically displayed and handled as unsigned ...
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.
On the 8086, 8088, and 80186, the result of an effective address that overflows 20 bits is that the address "wraps around" to the zero end of the address range, i.e. it is taken modulo 2^20 (2^20 = 1048576 = 0x100000). However, the 80286 has 24 address bits and computes effective addresses to 24 bits even in real mode.
The mass-market 8086 shipped in 1978. The 8086 was designed to be backward-compatible with the 8080 in the sense that 8080 assembly language could be mapped on to the 8086 architecture using a special assembler. Existing 8080 assembly source code (albeit no executable code) was thereby made upward compatible with the new 8086 to a degree. In ...
Read/write base address of FS and GS segments from user-mode. Available in 64-bit mode only. RDFSBASE r32 RDFSBASE r64: F3 0F AE /0 F3 REX.W 0F AE /0: Read base address of FS: segment. 3 Ivy Bridge, Steamroller, Goldmont, ZhangJiang: RDGSBASE r32 RDGSBASE r64: F3 0F AE /1 F3 REX.W 0F AE /1: Read base address of GS: segment. WRFSBASE r32 ...
The Intel 8086, Intel 8088, and Intel 80186 processors had 20 address lines, numbered A0 to A19; with these, the processor can access 2 20 bytes, or 1 MB. Internal address registers of such processors only had 16 bits.
An 8086 system, including coprocessors such as 8087 and 8089, and simpler Intel-specific system chips, [d] was thereby described as an iAPX 86 system. [7] [e] There were also terms iRMX (for operating systems), iSBC (for single-board computers), and iSBX (for multimodule boards based on the 8086-architecture), all together under the heading ...