[1] : The Free On-line Dictionary of Computing (27 SEP 03)

intel 8086
     
         a sixteen bit microprocessor chip used in early
        ibm pcs.  the intel 8088 was a version with an eight-bit
        external data bus.
     
        the intel 8086 was based on the design of the intel 8080 and
        intel 8085 it was source compatible with the 8080 with a
        similar register set, but was expanded to 16 bits.  the bus
        interface unit fed the instruction stream to the execution
        unit through a 6 byte prefetch queue, so fetch and execution
        were concurrent - a primitive form of pipelining 8086
        instructions varied from 1 to 4 bytes.
     
        it featured four 16-bit general registers, which could also
        be accessed as eight 8-bit registers, and four 16-bit index
        registers including the stack pointer.  the data
        registers were often used implicitly by instructions,
        complicating register allocation for temporary values.  it
        featured 64k 8-bit i/o or 32k 16 bit ports and fixed
        vectored interrupts.  there were also four segment
        registers that could be set from index registers.
     
        the segment registers allowed the cpu to access 1 meg of
        memory in an odd way.  rather than just supplying missing
        bytes, as most segmented processors, the 8086 actually shifted
        the segment registers left 4 bits and added it to the address.
        as a result, segments overlapped, and it was possible to have
        two pointers with the same value point to two different memory
        locations, or two pointers with different values pointing to
        the same location.  most people consider this a brain
        damaged design.
     
        although this was largely acceptable for assembly language,
        where control of the segments was complete it could even be
        useful then, in higher level languages it caused constant
        confusion e.g. near/far pointers.  even worse, this made
        expanding the address space to more than 1 meg difficult.  a
        later version, the intel 80386, expanded the design to 32
        bits, and "fixed" the segmentation, but required extra modes
        suppressing the new features for compatibility, and retains
        the awkward architecture.  in fact, with the right assembler,
        code written for the 8008 can still be run on the most recent
        intel 486.
     
        the intel 80386 added new op codes in a kludgy fashion
        similar to the zilog z80 and zilog z280.  the intel
        486 added full pipelines, and clock doubling like the
        zilog z280.
     
        so why did ibm chose the 8086 series when most of the
        alternatives were so much better?  apparently ibm's own
        engineers wanted to use the motorola 68000, and it was used
        later in the forgotten ibm instruments 9000 laboratory
        computer, but ibm already had rights to manufacture the 8086,
        in exchange for giving intel the rights to its bubble memory
        designs.  apparently ibm was using 8086s in the ibm
        displaywriter word processor.
     
        other factors were the 8-bit intel 8088 version, which could
        use existing intel 8085-type components, and allowed the
        computer to be based on a modified 8085 design.  68000
        components were not widely available, though it could use
        motorola 6800 components to an extent.
     
        intel bubble memory was on the market for a while, but
        faded away as better and cheaper memory technologies arrived.
     
        1994-12-23
     
     
see also:
microprocessor ibm pc intel 8088 intel 8080 intel 8085 source compatible 
register set prefetch pipelining register index registers 
stack pointer register allocation vectored interrupts segment registers brain damaged 
assembly language intel 80386 intel 486 op code zilog z80 
zilog z280 intel 486 pipeline clock doubling ibm 
motorola 68000 ibm instruments bubble memory displaywriter word processor 
motorola 6800 intel 

Intel Corporati >> I Words
Intel Corporati, definition of term: Intel Corporati
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Dictionary.com/intel 8086
...... Intel 8086 was based on the design of the Intel 8080 and. Intel 8085 ( ... 1 entry found for intel 8086.. intel 8086. <processor> A sixteen bit ... ..
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Intel 8086
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Intel 8086 - Wikipedia, the free encyclopedia
...An Intel 8086 Microprocessor. The 8086 is a 16-bit microprocessor chip ... 8086 visual microprocessor emulator. List of Intel microprocessors | ... ..
http://www.wikipedia.org/wiki/Intel_8086, score=82, date indexed=December 21, 2005, 9:43 pm

CCOM - Intel 8086 / 8088
...Intel 8088 / 8086 | Intel 80286 | Intel 80386DX/SX | MOS Technologies  ... Datenblatt:. Intel 8088. Intel 8086. Erscheinungsjahr :. Juni 1979. ... ..
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Intel 8086 - netlexikon
...Article in English: Intel 8086  . *Artículo en español: Intel 8086 y ... Weblinks * Intel Museum. (http://www.intel.com/intel/intelis/museum/ ... ..
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Intel 8086. Os melhores resultados para Intel 8086 você encontra no Nosecrets.
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Intel 8086 - OneLook Dictionary Search
...... "Intel 8086" is defined. General (1 matching dictionary). * Intel 8086 ... Additional searches for Intel 8086.... Search completed in 0.02 ... ..
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Intel 8086 - Wikipedia, the free encyclopedia
...An Intel 8086 Microprocessor. The 8086 is a 16-bit microprocessor chip ... 8086 visual microprocessor emulator. List of Intel microprocessors | ... ..
http://en.wikipedia.org/wiki/Intel_8086, score=67, date indexed=January 1, 2006, 1:59 am

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