Yes they do work with x86/x64 and Itanium systems but you would have to compile say BOINC and the tasks to call the appropriate libraries for the coprocessor(s). Unfortunately, it would not be just a simple plug and go.
I often recommend them for scientifc and modeling HPC grid designs as ClearSpeed fit perfectly in that sector. The guys who created them came from Cambridge University Science department (if I remember correctly).