The Xmos chips give the programmer virtual time sliced contexts over one or more hardware core(s). Say you have a 400 Mhz base clock and 4 threads, each one would see the wall clock time advance at 100 Mhz. This is useful for having concurrent realtime operations on each hardware thread w/o having to resort to trickery.
These chips are ideal for DSP, phased arrays and beam forming. Most of their devkits are centered around voice applications.