An important advantage of optical signal processing is the possibility of performing various operations in parallel. Among the techniques proposed for parallel optical signal processing, frequency division multiplexing (FDM) is a well-known approach, in which different operations are performed in multiple sub-channels associated with different frequency bands. Here, we demonstrate the possibility of performing parallel optical signal processing by frequency division multiplexing of the edge modes of a topological photonic structure. This leads to the realization of a multiple-input-multiple-output (MIMO) topological optical signal processor that is capable of performing several analog functionalities simultaneously, enhancing the speed of computation significantly. Our theoretical and experimental findings open up the venue towards the realization of a new generation of multi-functional topological optical signal processing systems that are ultra-fast, consume little power, and enjoy strong protection against disorder.