About OpenROAD#

OpenROAD is the leading open-source, foundational application forsemiconductor digital design. The OpenROAD flow delivers anAutonomous, No-Human-In-Loop (NHIL) flow, 24 hour turnaround fromRTL-GDSII for rapid design exploration and physical design implementation.

OpenROAD Mission#

OpenROAD eliminates the barriersof cost, schedule risk and uncertainty in hardware design to promoteopen access to rapid, low-cost IC design software and expertise andsystem innovation. The OpenROAD application enables flexible flowcontrol through an API with bindings in Tcl and Python.

OpenROAD is used in research and commercial applications such as,

• OpenROAD-flow-scriptsfromOpenROAD

• OpenLane fromEfabless

• Silicon CompilerfromZero ASIC

• HammerfromUC Berkeley

• OpenFASoC fromIDEA-FASoC for mixed-signal design flows

OpenROAD fosters a vibrant ecosystem of users through activecollaboration and partnership through software development and keyalliances. Our growing user community includes hardware designers,software engineers, industry collaborators, VLSI enthusiasts,students and researchers.

OpenROAD strongly advocates and enables IC design-based educationand workforce development initiatives through training content andcourses across several global universities, the Google-SkyWatershuttles alsoincludes GlobalFoundries shuttles, design contests and IC designworkshops. The OpenROAD flow has been successfully used to datein over 600 silicon-ready tapeouts for technologies up to 12nm.

Getting Started with OpenROAD-flow-scripts#

OpenROAD providesOpenROAD-flow-scriptsas a native, ready-to-use prototyping and tapeout flow. However,it also enables the creation of any custom flow controllers basedon the underlying tools, database and analysis engines. Please refer to the flow documentationhere.

OpenROAD-flow-scripts (ORFS) is a fully autonomous, RTL-GDSII flowfor rapid architecture and design space exploration, early predictionof QoR and detailed physical design implementation. However, ORFSalso enables manual intervention for finer user control of individualflow stages through Tcl commands and Python APIs.

Figure below shows the main stages of the OpenROAD-flow-scripts:

Here are the main steps for a physical design implementationusing OpenROAD;

• Floorplanning

  • Floorplan initialization - define the chip area, utilization

  • IO pin placement (for designs without pads)

  • Tap cell and well tie insertion

  • PDN- power distribution network creation

• GlobalPlacement

  • Macro placement (RAMs, embedded macros)

  • Standard cell placement

  • Automatic placement optimization and repair for max slew,max capacitance, and max fanout violations and long wires

• DetailedPlacement

  • Legalize placement - align to grid, adhere to design rules

  • Incremental timing analysis for early estimates

• ClockTreeSynthesis

  • Insert buffers and resize for high fanout nets

• Optimizesetup/holdtiming

• GlobalRouting

  • Antenna repair

  • Create routing guides

• DetailedRouting

  • Legalize routes, DRC-correct routing to meet timing, powerconstraints

• ChipFinishing

  • Parasitic extraction using OpenRCX

  • Final timing verification

  • Final physical verification

  • Dummy metal fill for manufacturability

  • Use KLayout or Magic using generated GDS for DRC signoff

Tapeouts#

OpenROAD has been used for full physical implementation in over600 tapeouts in SKY130 and GF180 through the Google-sponsored,EfablessMPW shuttleandChipIgnite programs.

Build OpenROAD#

To build OpenROAD tools locally on your machine, follow stepsfromhere.

Regression Tests#

There are a set of executable regression test scripts in./test/.

# run tests for all tools./test/regression# run all flow tests./test/regressionflow# run <tool> tests./test/regression<tool># run all <tool>-specific unit testscdsrc/<tool>./test/regression# run only <TEST_NAME> for <tool>cdsrc/<tool>./test/regression<TEST_NAME>

The flow tests check results such as worst slack against reference values.Usereport_flow_metrics[test]... to see all of the metrics.

% report_flow_metrics gcd_nangate45                       insts    area util slack_min slack_max  tns_max clk_skew max_slew max_cap max_fanout DPL ANT drvgcd_nangate45            368     564  8.8     0.112    -0.015     -0.1    0.004        0       0          0   0   0   0

To update a failing regression, follow the instructions below:

# update log files (i.e. *ok)save_ok <TEST_NAME># update "*.metrics" for tests that use flow testsave_flow_metrics <TEST_NAME> # update "*.metrics_limits" filessave_flow_metrics_limits <TEST_NAME>

Run#

openroad [-help] [-version] [-no_init] [-exit] [-gui]         [-threads count|max] [-log file_name] [-db file_name] cmd_file  -help              show help and exit  -version           show version and exit  -no_init           do not read .openroad init file  -threads count|max use count threads  -no_splash         do not show the license splash at startup  -exit              exit after reading cmd_file  -gui               start in gui mode  -python            start with python interpreter [limited to db operations]  -log <file_name>   write a log in <file_name>  -db <file_name>    open a .odb database at startup  cmd_file           source cmd_file

OpenROAD sources the Tcl command file~/.openroad unless the commandline option-no_init is specified.

OpenROAD then sources the command filecmd_file if it is specified onthe command line. Unless the-exit command line flag is specified, itenters an interactive Tcl command interpreter.

A list of the available tools/modules included in the OpenROAD appand their descriptions are availablehere.

Git Quickstart#

OpenROAD uses Git for version control and contributions.Get familiarised with a quickstart tutorial to contributionhere.

Understanding Warning and Error Messages#

Seeing OpenROAD warnings or errors you do not understand? We have compiled a table of all messagesand you may potentially find your answerhere.

License#

BSD 3-Clause License. SeeLICENSE file.