The performance of a radar receiver is greatly dependent on the presence of noise. The receiver should achieve the constant false alarm rate (CFAR) and the maximum probability of the target detection. The CFAR receivers are usually used in radar applications for the radar signal processing in case of unknown or time-varying background noise statistics, especially in cases when clutter or jamming signals are above the receiver threshold. CFAR automatically adjusts the threshold to prevent the threshold crossings. The paper deals with a software-based implementation of CFAR. The softwarebased CFAR processing was tested on various types of processors and processing times were compared. The best results were achieved using the dual-core AMD Athlon64 X2 4800+ using SSE2 instructions for processing.