IntermediateQuestion 110 of 112Source: Synopsys PrimeTime User Guide: Setting the ECO Options; Writing Change Lists

What does report_eco show you after a round of PrimeTime ECO fixes?

From PDVerse STA Mentor Guide · pdVerse Mentor Guide

By Tabish Iqbal · 9+ Years VLSI Physical Design Experience

Short Answer

There is no report_eco command in PrimeTime, so this question has a false premise. Before fixing, report_eco_options (PT) confirms the settings the fixer is allowed to use, and report_eco_library_cells (PT) lists the candidate cells it can swap in. After fixing, the actual log of what changed comes from write_changes -format text (PT), which prints every size_cell and insert_buffer edit applied in the session as a readable change list.

Technical Reference DiagramWhat does report_eco show you after a round of PrimeTime ECO fixes?
Two write_changes outputs from the same ECO session, a -format text change list with eleven readable entries (one size_cell flagged as applied to the wrong instance U445 instead of U455) next to the -format icctcl script handed to IC Compiler II.

Technical Explanation

  • PrimeTime has no single "show me what the ECO just did" report; a designer looking for that has to combine a before-check and an after-artifact instead.
  • report_eco_options (PT) verifies the ECO options currently in effect for the session, margins, dont_use restrictions, spare and filler cell names, before any fixing runs, not after.
  • report_eco_library_cells (PT) lists the alternative library cells available as ECO candidates, again a pre-fix check of what the fixer could use, not a record of what it actually used.
  • write_changes (PT) is what actually records the edits: it writes a change list describing every size_cell, insert_buffer, or removal applied during the session's ECO commands.
  • write_changes -format text (PT) writes that list in descriptive text meant for a human to read, while -format icctcl or -format eco (PT) write the same edits as a script for IC Compiler II or for replay in PrimeTime itself.
  • Reading the text change list before generating the icctcl or eco format for implementation is the real "did every fix land where intended" checkpoint, since write_changes (PT) is a read of the accumulated edits at the point it is called, not just a one-way commit.

Common Mistake

The Trap: Looking for a report_eco command to review the session's edits, not finding one, and skipping the review step entirely before implementing the ECO.

  • Generating write_changes -format icctcl (PT) straight away without first reading a -format text change list means an unintended edit, such as a size_cell applied to the wrong instance, goes to the physical design team unreviewed.

Follow-up Question & Model Response

If write_changes already writes the edits out, why call it twice, once in text format and again in icctcl format?

Candidate Model Response: The text format exists for a person to read, so it lists each edit in plain sentences without worrying about matching any downstream tool's script syntax. The icctcl format instead has to be an exact, replayable Tcl script that IC Compiler II can execute to legalize and re-route the same edits, so it is written in a completely different structure aimed at a tool, not a reviewer. Calling write_changes (PT) twice with different formats costs almost nothing since it is just printing the same recorded edit list two different ways. Skipping the text version to save one command means the first human review of the ECO happens only after the physical design team has already started applying it.

Practical Example

After an overnight session fixing eleven hold violations, write_changes -format text -output eco_review.txt (PT) lists eleven entries: nine insert_buffer calls and two size_cell calls, each tied to an instance name and a net. The signoff reviewer reads that file and catches that one size_cell entry was applied to U445 instead of the intended U455, a one-character typo, and the fix is corrected before write_changes -format icctcl (PT) hands the change list to IC Compiler II.

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