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Intel 8088
The Intel 8088 ("''eighty-eighty-eight''", also called iAPX 88)〔(iAPX 86, iAPX 88 user's manual )〕〔()〕〔(Official Intel iAPX 286 programmers' manual ) (page 1-1)〕 microprocessor is a variant of the Intel 8086. Introduced on July 1, 1979, the 8088 had an 8-bit external data bus instead of the 16-bit bus of the 8086. The 16-bit registers and the one megabyte address range were unchanged, however. In fact, according to the Intel documentation, the 8086 and 8088 have the same execution unit (EU)—only the bus interface unit (BIU) is different. The original IBM PC was based on the 8088.
==History and description==
The 8088 was designed in Israel, at Intel's Haifa laboratory, as with a large number of Intel's processors.〔''The Israel Test'', Encounter Books, 10 Oct 2013, George F. Gilder, page 100.〕 The 8088 was targeted at economical systems by allowing the use of an 8-bit data path and 8-bit support and peripheral chips; complex circuit boards were still fairly cumbersome and expensive when it was released. The prefetch queue of the 8088 was shortened to four bytes, from the 8086's six bytes, and the prefetch algorithm was slightly modified to adapt to the narrower bus.〔Specifically, the most obvious change is that the 8088 bus unit will prefetch a byte when it can i at least one byte of the queue is empty; the 8086 bus unit will not prefetch unless at least two of the six queue bytes are empty, so that it can prefetch a whole aligned 16-bit word, which it does in one bus cycle. The 8088, having an 8-bit external data bus, can only fetch one byte per bus cycle, so waiting to prefetch a whole word would have no benefit and would only delay, reducing the chance that the next instruction byte is already in the prefetch queue when it is needed.〕 These modifications of the basic 8086 design were one of the first jobs assigned to Intel's then new design office and laboratory in Haifa, Israel.
Variants of the 8088 with more than 5 MHz maximum clock frequency include the 8088-2, which was fabricated using Intel's new enhanced nMOS process called HMOS and specified for a maximum frequency of 8 MHz. Later followed the 80C88, a fully static CHMOS design, which could operate with clock speeds from 0 to 8 MHz. There were also several other, more or less similar, variants from other manufacturers. For instance, the NEC V20 was a pin compatible and slightly faster (at the same clock frequency) variant of the 8088, designed and manufactured by NEC. Successive NEC 8088 compatible processors would run at up to 16 MHz. In 1984, Commodore International signed a deal to manufacture the 8088 for use in a licensed Dynalogic Hyperion clone, in a move that was regarded as signalling a major new direction for the company.
When announced, the list price of the 8088 was US $124.80.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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