This paper presents aspects of parallelism of computations in processing of signals using digital signal processors (DSPs) with multi-issue assembler instructions. We present general features of the contemporary DSPs with special attention paid to the VLIW architecture. In order to illustrate the multi-issue instruction technique we analyze performance of the fixed-point Blackfin processor by means of chosen typical signal processing tasks realized using VisualDSP++ 4.5 environment with Software Development Kit 2.01. Aspects of the floating-point processing are analyzed using Sharc and TigerSharc processors.