FP11-B Floating-Point Processor

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The FP11-B was a FPP used in the PDP-11/45 and PDP-11/70 computers (KB11-A and KB11-B CPU variants thereof, respectively); it was the progenitor of the semi-standard FP11 floating point used in many PDP-11s.

It operated in parallel with the main processor, so that two instructions (one floating point, one regular) could be processed at the same time; unlike the later FP11-C Floating-Point Processor for these machines, it ran entirely asynchronously to the main CPU, and used a clock which was not synchronized to the basic CPU's clock.


It plugged into special pre-wired slots in the CPU's backplane, and included the following boards:

  • M8112 ROM and ROM Control
  • M8113 Exponent and Data Path
  • M8114 Fraction Data Path - High Order
  • M8115 Fraction Data Path - Low Order

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