4.1 BSD

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4.1 BSD
Logging into a 4.1 BSD system
Type: Multitasking, multiuser
Creator: CSRG
Architecture: VAX, theoretically portable
This Version: 4.1 (1981)
Date Released: 1981

This version of BSD addressed many of the performance shortcomings in 4.0 BSD that were brought up in a VMS vs BSD paper. Many of the changes are outlined in Bug fixes and changes in 4.1bsd. One of the big points of 4.1 is that it supported the VAX-11/750, which became a workhorse favorite of the DoD, which in turn led to DARPA grants to the CSRG to continue developing BSD. The 4.1 BSD kernel was systematically tuned up by Bill Joy until it could perform as well as VMS on several benchmarks.

The release would have been called 5BSD, but after objections from AT&T the name was changed; AT&T feared confusion with AT&T's UNIX System V.

Other features included:

  • job control
  • automatic kernel config
  • vfork()

4.1 BSD, June 1981 4BSD was upgraded to include many performance improvements, support for a new VAX model and autoconfiguration.

Once DARPA was funding the development of BSD, it lead to 2 big improvements from 4.1 to 4.2: the adddition of TCP/IP, and the new BSD Fast File System. These were beta-released in three intermediate versions: 4.1a included BBN's preliminary TCP/IP implementation; 4.1b included the new FFS; and 4.1c was an interim release of what became 4.2 BSD, during the last few months of its development.

Apparently 4.1a includes the BBN TCP/IP stack, but on a 750, it only can perform at 56kb on Ethernet, and maximizes the CPU to 100%, whereas Bill Joy's TCP/IP could get upwards of 700k/sec.

Getting this to run


A tape image for 4.1 has surfaced on bitsavers, named 4.1_BSD_19810710.zip The bootblock programs do not run under SIMH using the 4.0 BSD strategy, however it is possible to swap tapes when restoring the root slice, and then restoring the tars. Using this modified tape, I've created an installation guide Installing 4.1 BSD on SIMH.


There is two tape images on bitsavers 4.1C BSD 1 of 2, and 4.1C BSD 2 of 2. A much needed to revise guide is available Installing 4.1c BSD on SIMH.


These are what is available on the 1981 tape:

aardvark    banner      ching       lib         snake
adventure   bcd         cribbage    mille       snscore
advfiles    bogdict     fish        monop       trek
arithmetic  boggle      fortune     number      wump
backgammon  chess       hangman     quiz        zork


Bug fixes and changes in 4.1 BSD

Post 4.1 releases

4.1a This was a test release including TCP/IP and the socket interface. It saw a wide release, although it seems to have disappeared.

4.1b This was a test release, used only a Berkley and it includes the new Fast File System, using clustering for much improved performance, and contained the netw networking code.

4.1c 1982/1983 The third test release between 4.1BSD and 4.2BSD, it was distributed to about 100 sites and includes most 4.2 features except for the new signal facility. There is a detailed paper UNIX* System V and 4.1C BSD written by John Chambers & John Quarterman, that details 4.1c BSD.