This allows some flexibility in how the DSP is assigned and gives better PCI performance if you use the extra DSP chip. So if you are getting DAE error -6042 saying the PCI bus is too busy you would want to choose the 96 voice 3 DSP setting in this example.Using the extra DSP chip is also used with systems that are setup with the Avid Unity Network to help PCI performance. Using the 96 voice 2 DSP will give you more efficient DSP usage so you will have more chips available for plugins. So this would be the normal choice unless you are having the -6042 error occur.