MPICH is a freely available, portable implementation of MPI, a standard for message-passing for distributed-memory applications used in parallel computing. MPICH is Free Software and is available for most flavours of Unix (including Linux and Mac OS X) and Microsoft Windows.
The CH part of the name was derived from "Chameleon", which was a portable parallel programming library developed by William Gropp, one of the founders of MPICH.
The original implementation of MPICH (MPICH1) implements the MPI-1.1 standard. The latest implementation (MPICH2) implements the MPI-2.2 standard.
MPICH2 is one of the most popular implementations of MPI. It is used as the foundation for the vast majority of MPI implementations including IBM MPI (for Blue Gene), Intel MPI, Cray MPI, Microsoft MPI, Myricom MPI, OSU MVAPICH/MVAPICH2, and many others.
The mpich1 modules in CRC are deprecated!!
See the official website: MPICH