zilog z8000

1 definition found

zilog z8000 - Free On-line Dictionary of Computing (26 May 2007) :

  Zilog Z8000
  Z8000
  
     <processor> A microprocessor from Zilog introduced not
     long after the Intel 8086, but with superior features.  It
     was basically a 16-bit processor, but could address up to 23
     bits in some versions by using segment registers (to supply
     the upper 7 bits).  There was also an unsegmented version, but
     both could be extended further with an additional MMU that
     used 64 segment registers.
  
     Internally, the Z8000 had sixteen 16-bit registers, but
     register size and use were exceedingly flexible.  The Z-8000
     registers could be used as sixteen 8-bit registers (only the
     first half were used like this), sixteen 16-bit registers,
     eight 32-bit registers, or four 64-bit registers, and included
     32-bit multiply and divide.  They were all general purpose
     registers - the stack pointer was typically register 15,
     with register 14 holding the stack segment (both accessed as
     one 32-bit register for painless address calculations).
  
     The Z8000 featured two modes, one for the operating system
     and one for user programs.  The user mode prevented the user
     from messing about with interrupt handling and other
     potentially dangerous stuff.
  
     Finally, like the Zilog Z80, the Z8000 featured automatic
     DRAM refresh circuitry.  Unfortunately it was somewhat slow,
     but the features generally made up for that.  Initial bugs
     also hindered its acceptance (partly because it did not use
     microcode).  There was a radiation resistant military
     version.
  
     There was a later 32-bit, pipelined version, the Zilog Z80000
     .
  
     (1997-12-16)