Intel® Quartus® Prime Standard Edition User Guide: Design Compilation

ID 683283
Date 9/24/2018
Document Table of Contents Register Partition Inputs and Outputs

Use registers at partition input and output connections that are potentially timing-critical. Registers minimize the delays on inter-partition paths and prevent the need for cross-boundary optimizations.

If every partition boundary has a register as shown in the figure, every register-to-register timing path between partitions includes only routing delay. Therefore, the timing paths between partitions are likely not timing-critical, and the Fitter can generally place each partition independently from other partitions. This advantage makes it easier to create floorplan location assignments for each separate partition, and is especially important for flows in which partitions are placed independently in separate Intel® Quartus® Prime projects. Additionally, the partition boundary does not affect combinational logic optimization because each register-to-register logic path is contained within a single partition.

Figure 9. Registering Partition I/O

If a design cannot include both input and output registers for each partition due to latency or resource utilization concerns, choose to register one end of each connection. If you register every partition output, for example, the combinational logic that occurs in each cross-partition path is included in one partition so that it can be optimized together.

It is a good synchronous design practice to include registers for every output of a design block. Registered outputs ensure that the input timing performance for each design block is controlled exclusively within the destination logic block.