There are two main categories for the MPUs. The X1600 and the X2000. The X1600 can be thought of as best for lighter applications whereas the X2000 is best for the more advanced systems. The X1600s feature a 1 GHz core and the X2000 uses a dual core 1.2 GHz core. The X1600 comes in two versions, one with 32 MB and the 1600E with 64 MB of low power DDR2 memory.