In this paper we discuss the benefits of writing code for a specific processor and exploiting all its capabilities. We shows that in some situations it is possible to significantly reduce the time consumption by using SSE2, a Single Instruction Multiple Data (SIMD) extension available in new Pentium processors. Speed of the Harris operator is used for evaluation. All experiments are run on a Pentium 4 and the results are compared between ordinary C-code and code using SSE2. The purpose is not only to achieve a significant speed-up of the code, but also to benefit from SSE2 code with the least possible programming effort.