ICC2: 15. ECO and incremental requalification Cheat Sheet

This stage covers ECO and incremental requalification: saving a baseline, setting ECO mode, spare cell inventory, netlist-driven edits, placing and legalising ECO cells, freeze-silicon mapping, incremental routing, post-ECO DRC and fill, and the timing impact.

Sanity check cheat sheet

One row per command card. Read left to right: the check, the command that answers it, then what a healthy result, a result to review and a hard stop look like.

Card	Check and when	Command	Healthy	Review	Hard stop
E-01	Baseline saved Before the ECO	`save_block` `save_lib <lib>`	The block and library are saved under a named baseline, and the reports from it are kept.	A baseline is saved, but its reports were regenerated later.	There is no baseline to compare with or roll back to.
E-02	ECO mode Before edits	`set_app_options -name design.eco_freeze_silicon_mode -value true`	The mode matches the plan: a metal-only ECO uses freeze mode, and other ECOs leave it off.	The mode was changed mid-ECO, with a recorded reason.	The plan is metal-only, but the mode is not set.
E-03	Spare cell inventory Before tape-out	`add_spare_cells -cell_name spare -lib_cell {AND2 OR2} -num_instances <n>`	Spare types and counts are spread across the block as planned.	Spares are clustered by cell density only, and the owner has reviewed them.	Spare types or counts are missing for the planned ECOs.
E-04	Netlist-driven ECO After logic change	`eco_netlist -by_verilog_file eco.v -write_changes eco_changes.tcl` `source eco_changes.tcl`	The change script was reviewed and applied once, and physical-only cells were compared where relevant.	Timing ECO changes are included deliberately.	The script was applied unreviewed, or run twice.
E-05	ECO cell placement After edits	`place_eco_cells -eco_changed_cells` `legalize_eco_cells -cells $ecoCells -displacement_tolerance_level low` `check_legality`	All ECO cells are placed and legal, and displacement is small.	Existing cells were moved, and each move is listed.	ECO cells are unplaced or illegal.
E-06	Freeze silicon mapping Metal-only ECO	`place_freeze_silicon -cells {ECO1 ECO2}` `check_freeze_silicon`	Every ECO cell maps to a matching spare cell.	A script that replaces cells with logically equivalent ones was used and reviewed.	An ECO cell has no matching spare.
E-07	Incremental routing After placement	`route_eco -nets {net1 net2} -reroute modified_nets_only` `check_routes`	Only the modified nets were rerouted, with zero DRC, opens or shorts.	Nets outside the ECO changed, with a recorded reason.	Opens, shorts or DRC remain after routing.
E-08	DRC and fill after ECO After routing	`signoff_check_drc -auto_eco true` `signoff_create_metal_fill -remove_by_rule drc_auto`	Only the changed areas were rechecked, and fill shapes in conflict were removed.	The change exceeds the incremental threshold, so a full run is used.	Full signoff DRC was never rerun before hand-off.
E-09	Timing and ECO impact After DRC clean	`update_timing` † `report_timing` `report_eco_physical_changes`	Slack is within the project budget, and physical changes are small.	A few cells show large displacement, and each is reverted or approved.	Timing was not refreshed after the ECO.

Command cheat sheet

ICC2 commands. Angle brackets are placeholders, and values shown are examples, not project limits. A dagger (†) marks a command the notes behind this book do not fully cover; it is shown without options, so confirm it with man or help in your release.

Checkpoints
`save_block`	Saves the block to disk. Changes the session; record it.
`save_lib <lib>`	Saves the design library, since changes are in memory until saved.
`save_block -as <block>/<label>`	Saves a labelled version to roll back to.
ECO settings and spares
`set_app_options -name design.eco_freeze_silicon_mode -value true`	Enables freeze silicon ECO mode. Changes the session; record it.
`add_spare_cells -cell_name spare -lib_cell {AND2 OR2} -num_instances <n>`	Spare cells of each type spread over the placement area. Changes the session; record it.
`add_spare_cells -cell_name spare -num_cells {NAND2 20 NOR 15}`	Spare cells with different counts per type. Changes the session; record it.
Netlist-driven ECO
`eco_netlist -by_verilog_file eco.v -write_changes eco_changes.tcl`	Tcl editing commands from the difference against a golden netlist.
`source eco_changes.tcl`	Applies the reviewed edits. Changes the session; record it.
`size_cell <cell> -lib_cell <lib_cell>`	Resizes one cell. Changes the session; record it.
`add_buffer -object_list {net1} -lib_cell <buf>`	Buffers inserted on the listed nets. Changes the session; record it.
Place the ECO
`place_eco_cells -eco_changed_cells`	Places cells changed by ECO operations on free sites near connectivity.
`legalize_eco_cells -cells $ecoCells -displacement_tolerance_level low`	Legalises ECO cells with little movement.
`place_freeze_silicon -cells {ECO1 ECO2}`	Places ECO cells and maps them to spare cells.
`check_freeze_silicon`	Lists ECO cells without a matching spare cell.
Route and check
`route_eco -nets {net1 net2} -reroute modified_nets_only`	Incremental routing of modified nets. Changes the session; record it.
`check_routes`	Routing DRC, opens and antenna findings.
`check_legality`	Placement legality after the ECO.
`signoff_check_drc -auto_eco true`	IC Validator DRC on changed areas only.
`report_eco_physical_changes`	Shows displacement caused by sizing and buffering ECOs.