DSP, is a specialized microprocessor that has an architecture which is optimized for the fast operational needs of digital signal processing.
The goal of digital DSP signal processors is usually to measure, filter or compress continuous real-world analog signals. Most general-purpose microprocessors can also execute digital signal processing algorithms successfully.
We cannot use a general-purpose microprocessor to process signals very well, Add and subtract operations are performed quite simply by general-purpose microprocessors in a single or very few clock cycles. The multiply and divide operations are more complex. A digital multiply operation consists of a series of shift and add operations. Division, which is more complex.
General-purpose microprocessors are quite slow in performing multiply and divide operations. They will typically sequentially execute a series of shift, add, and subtract operations from their microcode to perform a single multiply operation, and may consume many cycles to complete.
The DSP performs multiplication in a single cycle by implementing shift and add operations in parallel. The circuitry is relatively complex and consumes a considerable number of transistors. The benefit is very fast multiplication, which is required for processing most digital signals. When general-purpose DSPs are not fast enough, the signal is either processed using analog circuits (which may have some drawbacks), or in specialized DSP hardware designed only for that task. This eliminates many of the benefits of a programmable DSP.
Digital signal processing algorithms typically require a large number of mathematical operations to be performed quickly and repeatedly on a series of data samples. Signals (perhaps from audio or video sensors) are constantly converted from analog to digital, manipulated digitally, and then converted back to analog form.