X!!Tandem is a parallel, high performance version of X!Tandem that has been parallelized via MPI to run on clusters or other non-shared memory multiprocessors running Linux. With the exception of the details related to MPI launch, it is run exactly as X!Tandem, and produces exactly the same results. It differs from Parallel Tandem in that the parallelism is handled internally, rather than as an external driver/wrapper.
5/18/11 X!!Tandem 10-12-01-1 released.
"X!!Tandem, an improved method for running X!Tandem on Collections of Commodity Computers", Bjornson et. al., Journal of Proteome Research, 2007. 
The paper reports results using X!!Tandem based on X!Tandem 10-01-01-4. However, newer versions of X!!Tandem are available that track the newest X!Tandem release.
Questions or comments, please contact firstname.lastname@example.org