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 for Motorola 6809
From The Free On-line Dictionary of Computing (30 December 2018) :

  Motorola 6809
      (MC6809) An eight-bit microprocessor from Motorola,
     The 6809 was a major advance over both its predecessor, the
     Motorola 6800 and the 6502.  The 6809 had two 8-bit
     accumulators, rather than one in the 6502, and could combine
     them into a single 16-bit register.  It also featured two index
     registers and two stack pointers, which allowed for some very
     advanced addressing modes.  The 6809 was source compatible
     with the 6800, even though the 6800 had 78 instructions and the
     6809 only had around 59 (including a SEX instruction).  Some
     instructions were replaced by more general ones which the
     assembler would translate and some were replaced by addressing
     The 6809 had one of the first multiplication instructions of the
     time, 16-bit arithmetic and a special fast interrupt.  But it
     was also highly optimised, gaining up to five times the speed of
     the 6800 series CPU.  Like the 6800, it included the undocumented
     HCF ({Halt and Catch Fire) bus test instruction.
     The Hitachi 6309 was a version with extra registers.  The
     6809 was used in the UK "{Dragon 32" personal computer and
     was followed by the Motorola 68000.
     Usenet newsgroup: news:comp.sys.m6809.
     Lennart Benschop  posted a
     emulator (originally called "usim") and a cross-assembler to
     Usenet newsgroup alt.sources on 1993-11-03.  Ray P. Bellis
      released a version 0.11.
     http://lennartb.home.xs4all.nl/m6809.html)">Benschop emulator (http://lennartb.home.xs4all.nl/m6809.html).

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