The first version of PVM was written during Summer of 1989 at Oak Ridge National Laboratory. It was not released, but was used in applications at the lab.
Version 2 was written from scratch during February 1991 at the University of Tennessee, Knoxville, and released in March of that year. It was intended to clean up and stablize the system so that external users could benefit.
After a year and a half of continuing research we felt that we had reached a limit in being able to add to PVM version 2. Version 3 was redesigned from scratch, and a complete rewrite started in September 1992, with first release of the software in March 1993. While similar in spirit to version 2, version 3 includes features that didn't fit the old framework - most importantly fault tolerance, better portability and scalability.