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Manufacturer: Digital Equipment Corporation
Architecture: PDP-11
Year Introduced: 1975
Bus Architecture: QBUS

The PDP-11/03, which initially shipped with the new LSI-11 CPU, marked a major change in the PDP-11 family in two ways:

  • it was the first PDP-11 to essentially use a microprocessor (although the LSI-11 chip set was 4 chips, not 1, it was effectively a microprocessor);
  • it was the first to use a new system bus, the QBUS, which used fewer lines (thus allowing cards which plugged into QBUS backplanes to have fewer contact fingers), thereby reducing costs.



1975. With the use of LSI semiconductor technology (the LSI-11 and LSI-11/2 processor), it was a compact implementation of the -11 architecture. It was limited though, to 32KW memory, only one processor operating mode, and limited floating-point instructions (the FIS). Available options: CIS, WCS, EIS/FIS.
The /03 used the new LSI bus, later known as the QBUS, and was aimed at the low-end market, as the successor of the /05. The slowest of the -11s (one third of the 11/20's performance).

A PDP-11/03 was also used as the diagnostic and control unit for the VAX-11/780's CPU; it would bootstrap the system.

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