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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.
The 8086 [3] (also called iAPX 86) [4] is a 16-bit microprocessor chip designed by Intel between early 1976 [citation needed] and June 8, 1978, when it was released. [5] The Intel 8088, released July 1, 1979, [6] 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 ...
Often, calculating a memory address involves more than one general-purpose machine instruction, which do not necessarily decode and execute quickly. By incorporating an AGU into a CPU design, together with introducing specialized instructions that use the AGU, various address-generation calculations can be offloaded from the rest of the CPU ...
enhanced microarchitecture used in the first two generations of the Itanium 2 microprocessor. Madison is the 130 nm version. Montecito enhanced McKinley microarchitecture used in the Itanium 2 9000- and 9100-series of processors. Added dual core, coarse multithreading, and other improvements.
This process is much faster than sending out an address, reading the opcode and then decoding and executing it. Fetching the next instruction while the current instruction is being decoded or executed is called pipelining. [8] The 8086 processor has a six-byte prefetch instruction pipeline, while the 8088 has a four-byte prefetch. As the ...
Such address translations are carried out by the segmentation unit of the CPU. The last segment, FFFFh (65535), begins at linear address FFFF0h (1048560), 16 bytes before the end of the 20 bit address space, and thus, can access, with an offset of up to 65,536 bytes, up to 65,520 (65536−16) bytes past the end of the 20 bit 8088 address space.
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.
The Intel 8086 and 8088 processors, with only 1 MB of memory and only 20 address lines, wrapped around at the 20th bit, so that address FFFF:0010 was equivalent to 0000:0000. [ 1 ] To allow running existing DOS programs which relied on this feature to access low memory on their newer IBM PC AT computers, IBM added special circuitry on the ...