1. QoR impact after logic synthesis

In this study, Focus was used to generate timing exceptions from RTL. These exceptions were verified using a property checking tool. The exceptions were read into a synthesis tool. QoR (WNS, total number of violations and instance count) was compared after logic synthesis with and without Focus exceptions. Run time data is for a Linux platform.
 

Design 1: 10K instances; 2 clocks

Exception Generation   Description False Paths Multicycle Paths FishTail Focus Generated 5 114 Focus Run Time 2 hours 6 hours 26 minutes

Logic Synthesis Data         Without Exceptions      With Exceptions    Worst Negative Slack (WNS) - 0.57 ns -0.26 ns No. of Setup Violations 688 272 Cell Area (1 nd202as = 2 C.U.A) 31,122 31,001 Total Instance Count 10,796 10,613 Compile Time 186 seconds 143 seconds

Design 2: 20K instances; 2 clocks

Exception Generation Description False Paths Multicycle Paths FishTail Focus Generated 39 29 Focus Run Time 3 minutes 7 hours 22 minutes Assertion Verification Verified 39 29 Failed 0 0 Timed-out 0 0

Logic Synthesis Data Without Exceptions With Exceptions Worst Negative Slack (WNS) -2.75 ns +0.02 ns No. of Setup Violations 729 0 Cell Area (1 nd202as = 2 C.U.A) 203,401 201,816 Total Instance Count 19,771 17,265 Design Compiler Run Time 4 minutes 2 minutes

Design 3: 50K instances; 1 Clock

Exception Generation Description False Paths Multicycle Paths FishTail Focus Generated 1059 93 Focus Run Time 2 hours 21 minutes 2 hours 48 minutes Assertion Verification Verified 1059 93 Failed 0 0 Timed-out 0 0

Logic Synthesis Data Without Exceptions With Exceptions Worst Negative Slack (WNS) -0.22 ns 0.0 ns No. of Setup Violations 64 0 Cell Area (1 nd202as = 2 C.U.A) 245,873 246,772 Total Instance Count 49,966 50,532 Compile Time 11 minutes 25 minutes

Design 4: 120K instances; 4 Clocks

Exception Generation Description False Paths Multicycle Paths FishTail Focus Generated 0 527 Focus Run Time 5 minutes 12 hours Assertion Verification Verified -NA- 95 Failed -NA- 0 Timed-out -NA- 432

Logic Synthesis Data Without Exceptions With Exceptions Worst Negative Slack (WNS) -0.91 ns -0.78 ns No. of Setup Violations 469 447 Cell Area (1 nd202as = 2 C.U.A) 261,982 262,667 Total Instance Count 1,18,142 1,18,247 Compile Time 27 minutes 31 minutes

2. QoR impact after physical synthesis

In this study, Focus was used to generate timing exceptions from RTL for the critical endpoints on a design. The critical endpoints were obtained after doing a quick synthesis of the RTL and seeing which endpoints did not meet timing. The exceptions were verified using Solidify and then read into Design Compiler. The netlist and SDC generated by Design Compiler were then fed into Physical Compiler. QoR data was compared for the same flow with and without Focus exceptions.

Design 5: 200K instances; 4 Clocks

Exception Generation Description False Paths FishTail Focus Generated 6266 Focus Run Time 3 hours 57 minutes

Physical Synthesis Data Without Exceptions With Exceptions Worst Negative Slack (WNS) -0.82 ns -0.03 ns No. of Setup Violations 682 19 Cell Area (1 nd202as = 2 C.U.A) 4,267,509 4,246,323 Total Instance Count 193,147 192,123 Net Length 11,841,259 10,634,302

3. QoR impact on static timing

In this study, the coverage of Focus generated exceptions was measured by taking taped-out designs and removing the timing exceptions that Focus was expected to catch. The number of timing violations and TNS with the timing exceptions removed was reported using PrimeTime. The endpoints that no longer met timing because timing exceptions were removed were written out. Exceptions for these endpoints were generated using Focus and then imported into PrimeTime. Now, the timing violations and TNS with Focus generated exceptions was reported. If the number of timing violations and TNS dropped to 0 with Focus exceptions then it demonstrated that we had caught all the timing exceptions that we were expected to catch. Runtime data for this study is on Solaris.

Design 6: 250K instances; 7 clocks

Exception Generation Description False Paths Multicycle Paths FishTail Focus Generated 4395 36 Focus Run Time 2 hours 9 minutes 9 hours 48 minutes

Static Timing Data Without Exceptions With Exceptions Total Negative Slack (TNS) 413 ns 18 ns No. of Setup Violations 814 105 Percentage Reduction in TNS - 96% Percentage Reduction in Violations - 87%

Design 7: 50K instances; 2 clocks

Exception Generation Description False Paths Multicycle Paths FishTail Focus Generated 79 6299 Focus Run Time 15 minutes 51 minutes

Static Timing Data Without Exceptions With Exceptions Total Negative Slack (TNS) 125993 ns 8166 ns No. of Setup Violations 63126 5966 Percentage Reduction in TNS - 94% Percentage Reduction in Violations - 91%