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PrimeTime Static Timing Analysis Overview

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PrimeTime Static Timing Analysis Overview | The Silicon Stack
EDA Tools & Industry Guidance · Part 5

PrimeTime: The Golden Standard for Timing Signoff

How static timing analysis replaces simulation for timing closure, and a real pt_shell signoff session.

In this post

  1. 1. Overview
  2. 2. Use Case & Who It's For
  3. 3. Where It Sits in the Design Flow
  4. 4. Installation & Licensing
  5. 5. Hands-On Example: A Timing Signoff Run
  6. 6. Key Takeaways

1.Overview

PrimeTime is Synopsys's static timing analysis (STA) tool and the industry's de facto golden signoff standard for timing closure. Rather than simulating a design with test vectors, STA exhaustively walks every timing path in the design — checking setup and hold against your clock constraints — without needing a single testbench.

The current PrimeTime Suite extends beyond pure timing into signal integrity, power, on-chip variation, and multiphysics effects such as IR-drop-aware and thermal-aware timing, all built on the same HSPICE-correlated analysis engine used for final signoff.

Note PrimeTime's HyperGrid technology distributes STA jobs across many machines with automatic, fine-grained partitioning, reporting full-quality, flat-netlist-accurate results at a fraction of the wall-clock time a single large STA run would otherwise take.

2.Use Case & Who It's For

PrimeTime is where physical design and timing closure engineers spend much of their sign-off time:

  • Final timing signoff before tapeout — the last, most trusted check that every path meets setup and hold across all corners
  • Signal integrity (crosstalk-aware) timing analysis at advanced nodes where coupling noise materially affects delay
  • Power analysis and leakage reduction through cell-swap and Vt-swap optimization, using the same timing data already computed for signoff
  • ECO (engineering change order) guidance — automatically sizing cells or inserting buffers to fix specific timing violations late in the flow

3.Where It Sits in the Design Flow

PrimeTime runs downstream of place-and-route, as the final gate before tapeout:

  1. A gate-level netlist and parasitics (extracted via a tool like StarRC) come out of place and route (ICC2 or Fusion Compiler)
  2. SDC constraints define the clocking, I/O timing, and exceptions the design must meet
  3. PrimeTime reads the netlist, parasitics, and constraints, then builds a full timing graph and reports setup/hold violations across all specified corners
  4. Where violations exist, ECO guidance recommends fixes (cell sizing, Vt swaps, buffer insertion) that the place-and-route tool then implements
  5. Once timing is clean across all corners, PrimeTime's signoff report is the artifact that supports the tapeout decision
Industry Insight Hierarchical ECO guidance can propagate a single fix across multiply-instantiated modules (MIMs) — if the same IP block is instantiated five times across an SoC, a correctly generalized ECO avoids fixing the same violation five separate times by hand.

4.Installation & Licensing

  1. Download the PrimeTime installer from Synopsys SolvNetPlus, under your organization's software license agreement
  2. Install on a supported 64-bit Linux distribution, typically alongside other Synopsys Galaxy Design Platform tools (Design Compiler, IC Compiler II, StarRC) sharing a common installation root
  3. Configure Synopsys's FlexLM-based license server (synopsys.lic or an organization's shared license server) and set the SNPSLMD_LICENSE_FILE environment variable
  4. Source the environment setup so pt_shell or dc_shell -t (interactive Tcl shells) resolve on PATH
  5. Cloud-based HyperGrid distributed analysis requires additional licensing and infrastructure setup through Synopsys Cloud, on top of a standard PrimeTime license

5.Hands-On Example: A Timing Signoff Run

A minimal PrimeTime signoff session, run interactively through pt_shell:

# pt_signoff.tcl - basic setup/hold signoff check
set_app_var link_library {typical.db}
set_app_var target_library {typical.db}

read_verilog netlist.v
current_design top
link_design

read_sdc constraints.sdc
read_parasitics netlist.spef

update_timing

report_timing -delay_type max -path_type full_clock -nworst 5
report_constraint -all_violators

report_constraint -all_violators is usually the first thing a timing engineer checks — it summarizes every path that fails setup or hold, sorted by worst negative slack, so effort goes to the paths actually blocking tapeout rather than paths that already comfortably pass.

Tip Run a quick update_timing after every SDC or netlist change and re-check report_constraint -all_violators before diving into full-path debug — it's easy to chase a violation that a subsequent constraint fix already resolved.

Recap

  • PrimeTime is Synopsys's STA signoff tool — exhaustive path checking, no testbench required.
  • It's the last gate before tapeout: timing, signal integrity, power, and variation-aware analysis.
  • HyperGrid distributes large STA runs across machines with full flat-netlist accuracy.
  • Core flow: read netlist/SDC/parasitics → update_timing → report_constraint -all_violators.
Next Up · Part 6

Design Compiler — Synopsys's RTL synthesis engine, and how it turns SystemVerilog into a gate-level netlist.

EDA Tools & Industry Guidance · Series
← JasperGold Design Compiler →
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