DSP processors are in general very I/O balanced processors. This means they offer a variety of high speed serial and parallel peripheral interfaces. These interfaces are ideally designed in a way, that they can be operated with very low or none overhead impact to the processor core, leaving enough CPU time for running the OS and processing the incoming or outgoing data.
Perhaps you rarely face it, but once you do, you surely know what's wrong: lack of free memory, or Out of Memory (OOM). The results are typical: you can no longer allocate more memory and the kernel kills a task (usually the current running one).