In this paper, a real-world signal and power integrity problem due to the switching noise of buck converter IC coupling to a high-speed signal line in a server system is studied. The rapid switching field effect transistors (FETs) of the voltage regulator module (VRM) are the main source of the performance degradation on the nearby signal lines. A simplified mock-up simulation setup is proposed based on the actual board design to investigate the coupling mechanism of the VRM noise. The mechanism of the switching noise coupling is explained with the phenomenon of capacitive and inductive coupling. Based on this finding, the solutions will be identified as decreasing the inductive coupling by optimizing the board layout.