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The KB11-C CPU is the later CPU for the PDP-11/70; it is basically the same as the earlier KB11-B CPU, except that it takes the later synchronous FP11-C Floating-Point Processor, instead of the asynchronous earlier FP11-B Floating-Point Processor


The basic KB11-C consisted of fifteen hex boards, basically the same board set as the earlier KB11-B, except that two boards:

  • M8133 ROM and ROM Control
  • M8138 System Status Registers

were replaced with the:

  • M8123 ROM and ROM Control
  • M8138-YA System Status Registers


Note: The DEC documentation contains an error here. The "PDP-11/70 Maintenance and Installation Manual", EK-11070-MM-002, refers to the M8133 in board lists for the KB11-C, where the M8123 is meant (e.g. pg. 1-3). However, the KB11-C Engineering Drawings include the drawings for the M8123, not the M8133; other manuals also confirm that the KB11-C uses the M8123 (see, for example, the KB11-A,D Maintainence Manual, EK-KB11A-MM-004, pg 1-1).

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