On July 9, jkunz(a)unixag-kl.fh-kl.de wrote:
  Some recent version (maybe 1.5, at least -current) of
NetBSD will run on
 that beast, but the best choice would be SunOs 4.1.3 That is the OS
 this machine was build for. Is is a decent 4.2BSD UNIX derivate with
 4.3BSD and SysV enhancements. 
  For SunOS, I'd suggest 4.1.4.
  Very recent NetBSD will run nicely on that machine as well.
        -Dave McGuire