You are not going to design a 224 Gbps system using a free tool, but you may gain insight into how to solve a problem at 224 Gbps using a free tool. I will share my top five favorite free SIPI tools, which I think every engineer needs to have to help them accelerate up the learning curve. These include S-parameter viewers, 2D field solvers, 3D field solvers, and circuit simulators. I might even throw in a bonus tool or two.