Multi-Threshold Leakage Power Optimization

TCL script for post-synthesis leakage power minimization using multiple cell libraries [LVT (Low), SVT (Standard), HVT (High)]. Starting circuit netlist is composed of all LVT cells.

Description

The function to perform cell swapping can be invoked as multiVth slackThreshold maxPaths, its arguemnts being:

• slackThreshold: Timing paths with slack < slackThreshold are defined as violating paths. Allowed values may range from 0 to 0.25 ns.
• maxPaths: Maximum number of violating paths for each endpoint in the circuit. Allowed values may range from 1 to 10000.

Example usage: multiVth 0.10 100

Constraints

The following additional constraints are imposed:

• Worst slack must be positive.
• For each endpoint of the circuit, the number of violating paths must be < maxPaths.
• Logic gates must keep the same cell footprint (i.e. same strength), during the optimization loop.
• Run time (measured using the TCL clock command on the remote server) must be < 5 minutes.

Project Structure:

• src: Directory containing TCL scripts:
  • BasicSwap.tcl: Basic algorithm which:
    • (1) ranks cells in the circuit netlist based on descending slack;
    • (2) replaces the top 50% LVT (highest slack) cells with HVT cells;
    • (3) replaces the remaining 25% LVT cells with SVT cells.
  • OptimizedSwap.tcl: More advanced algorithm which:
    • (1) ranks cells in the circuit netlist based on descending slack;
    • (2) swap highest slack cells to HVT, and if doing so introduces a timing violation, the cell is reverted to its original type;
    • (3) for cells which were reverted, try swapping to SVT, and if introducing a timing violation, revert back.
• SYN Contest.pdf: Report containing both algorithm's results, which were able to save at least 60% leakage power in both benchmarks (c1908 and c5315).

More details can be found in the report SYN Contest.tcl.

License

This project is licensed under the MIT License - see the LICENSE file for details.