2.2.4. Technique 4: Lock Down PR Boundary Ports
If you do not lock down the PR boundary ports (IOPORTs), the Intel® Quartus® Prime Fitter tends to distribute these ports based on the source and destination placement, as Floorplan 8 and Floorplan 9 show in Distribution of Ports with Locked and Unlocked I/O Ports. While this distribution might be the best placement for the current compiled persona, it might not be suitable for another persona, and could even negatively affect the performance.
Therefore, it is best to lock down the PR boundary ports to increase consistent performance across different PR personas, although this might not be the best placement for a dedicated persona. When using this method, the PR region appears as the entire chip with thousands of I/O ports along the boundary, which is more suitable for multiple different personas, as Floorplan 10 shows.