Performing signal integrity (SI) analysis on integrated circuit designs is becoming increasingly important as these designs increase in size and complexity. Dividing a design into blocks can simplify the resulting analysis. Additionally, such blocks can be replaced with timing models, which provide a compact means of exchanging interface timing information for the blocks. To further increase the speed and accuracy of SI analysis, enhanced interface logic models (SI-ILMs) can be used. An SI-ILM can include cells in timing paths that serve as the interface between the block and other parts of the design. The SI-ILM can also include internal nets that have cross-coupling effects on interface nets and nets outside the block. By including these internal nets, SI analysis at the top-level can be both fast and accurate.