Use Physical Optimization - 2021.2 English

UltraFast Design Methodology Guide for Xilinx FPGAs and SoCs

Document ID
UG949
Release Date
2021-11-19
Version
2021.2 English

Physical optimization (phys_opt_design) automatically replicates the high fanout net drivers based on slack and placement information, and usually significantly improves timing. Xilinx recommends that you drive high fanout nets with a fabric register (FD*), which is easier to replicate and relocate during physical optimization.

In some cases, the default phys_opt_design command does not replicate all critical high fanout nets. Use a different directive to increase the command effort: Explore, AggressiveExplore or AggressiveFanoutOpt. Also, when a high fanout net becomes critical during routing, you can add an iteration of phys_opt_design to force replication on specific nets before trying to route the design again. For example:

phys_opt_design -force_replication_on_nets [get_nets [list netA netB netC]]