Confusion understanding digital signal processor?
The staple processor instruction of specialized DSP processors is a multiply-accumulate instruction. The vector multiplication and summation are performed in a single command fetch, it's a sort of SIMD (but not exactly). Only advanced MCU's have this instruction in their command set. Hence the advantage of DSP processors over general-purpose MCU's w.r.t. ALU performance on typical signal-processing operations, even when comparable technological process are used in their manufacturing. The same for FPGA devices with internal DSP blocks. In short, less command fetch cycles, higher performance.