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M7135 MicroVAX I Data Path Module (DAP)

The KD32 (also called the KA610) was the CPU in the MicroVAX I, and its workstation form, the VAXstation I. It is microcoded and pipelined, and is contained on two quad-height PCBs:

  • Data Path Module (DAP) M7135
  • Memory Controller Module (MCT) M7136

(The VAXstation I uses a later variant, the KD32-AB; it uses the M7135-YA instead of the basic M7135. The two differ in which floating point data formats they support.)

The two modules of the MicroVAX I intercommunicate over the CD interconnect of the H9278-A backplane, and an over the back flat cable; the data paths there are the Memory Control Bus (MCB - over the CD interconnect) and the Memory Data Bus (MDB - over the flat cable). The KD2 uses the QBUS as both its main memory and I/O bus.

The KD32 contains:

  • An interface to the Q22 bus (supports block mode transfers, and up to four megabytes of memory)
  • An 8 KB direct-mapped cache
  • A 512 entry (long-word) virtual memory translation buffer
  • A 10 ms non-programmable interval timer
  • An interface to a console asynchronous serial line (available baud rates: 300, 1200, 9600, 19200)
  • An 8 KB or 16 KB bootstrap EPROM
  • Interfaces to the front control panel and rear patch panel assembly


M7136 MicroVAX I Memory Controller Module (MCT)

The KD32 uses standard Q22 QBUS memories (as used in QBUS PDP-11s).

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