Why a separate Spice program?
Many PC board layout programs come with some sort of Spice simulator. To use the simulator, you often must replace the parts in your PC board schematic with parts from a separate library of simulation parts. And remove connectors, digital parts, etc. you don’t want to model. And add parts to model component imperfections (resistance of inductors, etc.) plus special parts like Spice signal sources and so forth. Then run simulations using a user interface that was designed for easy PCB layout, not for simulation. 5Spice is totally aimed at Spice simulation, including its schematic features (see the White Paper for details). Since experienced circuit designers normally simulate only a small portion of a large circuit, it is often quicker to draw just that portion in 5Spice and start simulating. Plus it is much easier to document your simulation work in 5Spice. Download it and see.
