PDP-11 Extended Instruction Set

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The Extended Instruction Set is an extension to the basic PDP-11 instruction set; it includes hardware multiply and divide, and also multi-bit shifts. The exact instructions include in the EIS are:

  • MUL
  • DIV
  • ASH
  • ASHC

It was not available on the earliest PDP-11 models (the PDP-11/20 and the PDP-11/05); it was available as an option for the PDP-11/40 and the PDP-11/03; it was standard on all other PDP-11 models.