High-Fanout Net Synthesis

During placement and optimization, ICC does not buffer clock nets as defined by the create_clock cmd, but it does , by default, buffer other high-fanout nets, such as resets or scan enables, using a built-in high-fanout synthesis engine.

Before running high-fanout net synthesis during the place_opt step,  define the buffering options by using the set_ahfs_options cmd.

During high-fanout net synthesis, ICC automatically analyzes the buffer trees to determine the fanout thresholds by default, and then it removes and builds buffer trees.

The high-fanout synthesis engine does not buffer nets that are set as ideal nets or nets that are disabled with respect to design rule constraints.

As an alternative to performing high-fanout net synthesis during place_opt, you can use the create_buffer_tree cmd to run standalone high-fanout net synthesis.

To get onformation about the buffer trees in your design, use the report_buffer_tree cmd.

To remove buffer trees from your design, use the remove_buffer_tree cmd.