Many designs consist of parts that run at different clock rates. For the fastest part, the system clock period is used. For the remaining parts, the clock period is an integer multiple of the system clock period. It is important that downstream tools know what speed each part of the design must achieve. With this information, efficiency and effectiveness of the tools are greatly increased, resulting in reduced compilation times and improved hardware realizations. The division of the design into parts, and the speed at which each part must run, are specified in the constraints file using multicycle path constraints.