The LTSpice IV Simulator

It is an honor to write a preface for Gilles Brocard. I appreciate his work writing this book and hope you benefit fromhis labors.LTspice has been fun to write. It let me implement a number of numerical methods that make LTspice better thantraditionalSPICE programs: a new numerical integration method, node reduction, a native circuit element that behaveslike a power MOSFET, and new time step size control to name a few.The biggest recent advance in LTspice was when it went multi-threaded in 2008. We found it easy to distribute thecomputations over multiple cores but challenging to make the simulation actually run faster. The problem was thatthe LTspice object code had been so optimized (much had already been implemented in optimized assembly language)that it didn't take very many microseconds per timestep and that was a short time compared to how well onecan synchronize multiple threads. That's when we developed a means to dynamically adjust each threads' cache sizeto stochastic cool the threads to keep the work load spread evenly. Another important technique introduced at thattime was code generation that generates an assembly listing optimized for your circuit. Then that code is assembledand linked by LTspice for execution. This self-authoring code is generated typically every few seconds during the simulationto help your circuit execute close to the theoretical flop limit of a modern CPU. That's why LTspice IV is fast.But all this is for a purpose. I believe SPICE has impacted mankind more than any other simulator. Writing a betterSPICE is important. LTspice offers you the ability to rapidly prototype your designs so that you understand them betterand even develop intuition. von Brocard, Gilles