The Microsoft HPC solution comes with an enhanced MPI stack. For sure, it is not the only MPI stack that runs on windows.  ANL has an mpich2 mpi stack, so does HP.  How does MSMPI differ from the ANL one, of which it is based on? 

1.  MSMPI comes in both 32bit and 64bit.  That means, you can develop on 32bit windows vista, xp, windows 2008, and 64bit of these OS.   Even if you are on 32 bit OS, you can cross compile 64 bit code that would run on the computing cluster.

2.  The computing cluster only comes in 64 bit, however it will run both 64  bit and 32 bit code.

3. MSMPI, according to the product group, does authentication through the job scheduler.  So, while you can develop and run on a single machine, you won't be able to run mpiexec cross several work stations without the compute cluster software (job scheduler,etc)   MPICH from ANL will allow you to do it.

4.  MSMPI also supports the IB network direct driver to support that very exciting, super short latency advantage that got MSMPI #23 on the top 500 list.

5.  MSMPI is fully compatible with MPICH 2 API.

6.  MSMPI has many additional bug fixes, and performance enhancements.

Next time, we'll go over HPC compiler options on Microsoft windows.