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由IBM公司与Motorola公司推出一种RISC微处理器

资料来源 : Free On-Line Dictionary of Computing

PowerPC
     
         (PPC) A {RISC} {microprocessor} designed
        to meet a {standard} which was jointly designed by {Motorola},
        {IBM}, and {Apple Computer} (the PowerPC Alliance).  The
        PowerPC standard specifies a common {instruction set
        architecture} (ISA), allowing anyone to design and fabricate
        PowerPC processors, which will run the same code.  The PowerPC
        architecture is based on the IBM {POWER} architecture, used in
        IBM's {RS/6000} {workstation}s.  Currently {IBM} and
        {Motorola} are working on PowerPC chips.
     
        The PowerPC standard specifies both 32-bit and 64-bit data
        paths.  Early implementations were 32-bit (e.g. {PowerPC
        601}); later higher-performance implementations were 64-bit
        (e.g. PowerPC 620).  A PowerPC has 32 integer {registers} (32-
        or 64 bit) and 32 {floating-point} (IEEE standard 64 bit)
        {floating-point} registers.
     
        The POWER CPU chip and PowerPC have a (large) common core, but
        both have instructions that the other doesn't.  The PowerPC
        offers the following features that POWER does not:
     
        Support for running in {little-endian} mode.
     
        Addition of single precision {floating-point} operations.
     
        Control of branch prediction direction.
     
        A hardware coherency model (not in Book I).
     
        Some other {floating-point} instructions (some optional).
     
        The real time clock (upper and lower) was replaced with the
        time base registers (upper and lower), which don't count in
        sec/ns (the decrementer also changed).
     
        64-bit instruction operands, registers, etc. (in 64 bit
        processors).
     
        See also {PowerOpen}, {PowerPC Platform} (PReP).
     
        {IBM PPC info
        (http://fnctsrv0.chips.ibm.com/products/ppc/index.html)}.
     
        {(gopher://info.hed.apple.com/)}, "Apple Corporate News/"
        (press releases), "Apple Technologies/" and "Product
        Information/".  {(gopher://ike.engr.washington.edu/)}, "IBM
        General News/", "IBM Product Announcements/", "IBM Detailed
        Product Announcements/", "IBM Hardware Catalog/".
     
        {Usenet} newsgroups: {news:comp.sys.powerpc},
        {news:comp.sys.mac.hardware}.
     
        ["Microprocessor Report", 16 October 1991].
     
        (1994-09-30)