To make an efficient system, it is important to choose the FPGA configuration mode that best matches the system's requirements. Each configuration mode dedicates certain FPGA pins and can temporarily use other multi-function pins during configuration. These multi-function pins are then released for general use when configuration is completed. Similarly, the configuration mode can place voltage restrictions on an FPGA I/O bank. Several different configuration options are available, and while the options are flexible, there is often an optimal solution for each system. Several topics must be considered when choosing the best configuration option including: overall setup, speed, cost, and complexity. These topics and others are discussed in this chapter.