[[Image:FDTD57.png|thumb|350px|EM.Tempo's Run dialog.]]
[[Image:FDTD58.png|thumb|500px|EM.Tempo's Simulation Engine Settings dialog]]
[[Image:FDTD66.png|thumb|500px350px|EM.Tempo's output window.}}]]
An FDTD simulation involves a number of numerical [[parameters]] that can be accessed and modified from the FDTD Engine Settings Dialog. To open this dialog, select '''Menu > Simulate > Simulation Engine Settings... '''or open the '''Run Dialog''', and click the '''Settings''' button next to the engine dropdown list.
The serial CPU solver is [[EM.Cube]]'s basic FDTD kernel that run the time marching loop on a single central processing unit (CPU) of your computer. The default option is the multi-core CPU solver. This is a highly parallelized version of the FDTD kernel based on the Open-MP framework. It takes full advantage of a multi-core, multi-CPU architecture, if your computer does have one. The GPU solver is a hardware-accelerated FDTD kernel optimized for CUDA-enabled graphical processing unit (GPU) cards. If your computer has a fast NVIDIA GPU card with enough onboard RAM, the GPU kernel can speed up your FDTD simulations up to 50 times or more over the single CPU solver.
For structures excited with a plane wave source, there are two standard FDTD formulations: '''Scattered Field '''(SF) formulation and '''Total Field - Scattered Field''' (TF-SF) formulation. [[EM.Cube]]'s [[FDTD Module|FDTD moduleTempo]] offers both formulations. The TF-SF solver is the default choice and is typically much faster than the SF solver for most problems. In two cases, when the structure has periodic boundary conditions or infinite CPML boundary conditions (zero domain offsets), only the SF solver is available. The other sections of the FDTD Simulation Engine Settings dialog will be described next in the context of [[Waveforms and Discrete Fourier Transforms]].
===Running A Wideband FDTD Simulation===