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Logging into an Ultrix 4.0 system
Type: Multi-tasking, multi-user Unix
Creator: Digital Equipment Corporation
Architecture: PDP-11, VAX, DECStation/DECsystem (RISC)
This Version: 4.5 for VAX and DECStation (1995)
Date Released: ULTRIX-11: 1982, ULTRIX-32: 1984

ULTRIX was DEC's official UNIX for VAX, PDP-11 and DECStation/DECsystem (RISC) equipment.


ULTRIX-11 was available for the PDP-11 and can be obtained up to version 3.1 from the TUHS archive (below). It will run under SIMH (and other PDP-11 emulators).

These are the known ULTRIX-11 versions and predecessors:

  • 1981: Unix/v7m V2.1
  • 1982/83: V7M-11 V1.0 (= ULTRIX-11 V1.0)
  • 1984: ULTRIX-11 V2.0
  • 1986: ULTRIX-11 V3.0
  • 1987: ULTRIX-11 V3.1 (last version)


ULTRIX-32 (from version 4.0 onwards called: ULTRIX/VAX) for the VAX was derived from 4.2 BSD with some influences from SYSV and included support for specific DEC technologies. The latest version is 4.5 from 1995. Earlier versions of ULTRIX-32 are available from TUHS. It will run under the VAX simulator in SIMH.

Timeline of the main VAX versions:

  • 1984: V1.0
  • 1986: V2.0
  • 1988: V3.0
  • 1990: V4.0

DEC MIPS-based Computers

ULTRIX/RISC for DECstation and DECsystem computers is not available from TUHS. The latest version is 4.5 from 1995. This version will also run, (Including CDE + X11!) under GXemul.

Y2K compatibility

It's been confirmed that 4.0 is NOT Y2K compatible... Not many UNIX from the 1990's or prior are so it's really no surprise...

Running ULTRIX

SIMH will run Ultrix. Many simulators -if not all- of supported VAX computers are known to work.

Installation instructions for SIMH can be found at:

See also

External links