What-If Design Software LLC, Harrisburg, PA, offers AS/SIST signal integrity modeling and simulation software for pre-layout analysis of PCB-based high-speed digital designs. The software is used to eliminate problems such as reflections, cross talk, and lossy MTL effects in designs from basic single-board layouts to differential signal, system-level multiboard layouts. It contains a fast SPICE engine with specialized RLGC models, 2D+ field solver, IBIS-to-SPICE converter, schematic capture, pulse train generator, eye diagram analysis, waveform analyzer, and other functions and has been validated in practice against >2.5 Gbps differential serial data rate paths and 15 ps rise-time systems.