Reliability and performance of the parallel processing system greatly depends upon the topology of its interconnection network through which all processors are attached to themselves or to its memory modules necessary in parallel and efficient computation. In this research paper an already existing class of interconnection networks i.e. PM2I has been analyzed extensively for their better performance and hence new topology of gamma networks (member of PM2I class of interconnection networks) i.e. Gamma Minus Network has been evolved and its terminal reliability is analyzed for its performance check. Also, the achieved terminal reliability has been compared with terminal reliability of existing gamma networks. The comparison results prove that the new gamma minus networks has better reliability performance than gamma networks. As it has shortest path from source to destination, so it possess less delay with disjoint minimum path set availability which has not been possessed by gamma network.