The primary component is a general purpose circuit simulator. It performs nonlinear dc and transient analyses, fourier analysis, and ac analysis. Spice compatible models for the MOSFET (level 1-7), BJT, and diode are included in this release.

Gnucap is not based on Spice, but some of the models have been derived from the Berkeley models.

Unlike Spice, the engine is designed to do true mixed-mode simulation. Most of the code is in place for future support of event driven analog simulation, and true multi-rate simulation.