Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO Anne Yue

Transcription

1 Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO Anne Yue Synapse Design 2200 Laurelwood Rd. Santa Clara, CA 95054

2 Abstract This paper describes and compares the current EDA tools for STA, timing closure and timing ECO. In-depth studies on ETS, PrimeTime & Dorado let us understand the can/cannot of the tools. Proven-in-silicon workarounds are efficient for a faster timing closure. 3 solutions are shared in this paper to solve the left-over issues from PrimeTime ECO tool. One of the solutions(upsizing DFF) will be Enhancement features in future PrimeTime release( ). Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 2

3 Agenda Challenges for SOC Timing Closure Who Can Help on STA? Who Can Help on Timing ECO? Solutions with Clock Path ECO Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 3

4 Challenges for SOC Timing Closure ASIC design size increasing exponentially every year. 20 million instance designs last year. 65 million instance designs this year. With 32nm & less technology, temperature inversion and power related analysis bring in more PVT corners for timing STA. One ECO loop can take 3~5 days. Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 4

5 Who Can Help on STA --- ETS & PrimeTime ETS(Encounter Timing System) --- Cadence timing signoff tool PrimeTime --- Synopsys timing signoff tool ETS & PrimeTime are both silicon-proven timing signoff tools. ETS & PrimeTime can work interleave with implementation tools from other companies. Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 5

6 ETS vs. PrimeTime on Constraints The sdc coding style for clock-group related constraints matters to ETS & PrimeTime. ETS will interpret differently than PrimeTime on some clock-group definition. PrimeTime is more robust than ETS on this. With different clock-group understandings, ETS & PrimeTime will give out different sets of report. Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 6

7 ETS vs. PrimeTime on Design Slack If feed with the same quality(good) constraints, slack difference between ETS vs. PrimeTime DMSA ps with setup, 20ps with hold PrimeTime is more pessimistic than ETS. In some case ETS cannot report max_tran violation which PrimeTime reported. Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 7

8 ETS vs. PrimeTime on ECO PrimeTime DMSA can generate ECO.tcl for setup/hold/max_trans/max_fanout/max_cap DMSA MCMM features very helpful on timing closure with PVT corners/modes ETS ECO feature is under-construction. Hold time ECO is in place. No setup ECO. ETS is about 2~4 years behind PrimeTime on timing ECO. Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 8

9 Who Can Help on Timing ECO --- PrimeTime & Dorado PrimeTime is with fix_eco_timing & fix_eco_drc Same license as PrimeTime & PrimeTime-SI Dorado is a 100% ECO tool. Dorado does not have build-in timing engine. Instead, it has ECO-specific engine. Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 9

10 Dorado in ECO Dorado is with ECO for: setup/hold/max_trans/max_cap/max_fanout Dorado can generate eco.tcl & eco.def. The incremental.def file will serve as guidance for BackEnd tool ECO legalization, which increase the possibility of ECO process convergence. Clock ECO is the highlight for this tool. Remove buffers for setup fix. A new tool means the tool setup overhead efforts for design team. Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 10

11 PrimeTime in ECO fix_eco_timing can do: -- on Data Path 21 o upsize/downsize cells o insert buffer fix_eco_timing cannot do: o remove cells. o change clock path(clock Path 1 & Clock Path 2) Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 11

12 PrimeTime DMSA ECO --- Can & Cannot Data Path 21 DFF 2 DFF 1 Clock Path 2 Clock Path 1 Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 12

13 PrimeTime DMSA ECO --- fixed & left over Hold Violations : 99 ~ 100% good job! setup Violations : 85 ~ 90% DMSA ECO did very good job on cell-sizing base on MCMM timing analysis. But launch/capture clock path are untouched by the tool. Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 13

14 Before fix_eco_timing: After fix_eco_timing: Setup violations Total reg->reg reg->out in->reg in->out C2C * -> * WNS TNS NUM Hold violations C2C * -> * WNS TNS NUM Setup violations Total reg->reg reg->out in->reg in->out C2C * -> * WNS TNS NUM No hold violations found Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 14

15 How to fix the DMSA ECO left over violations? No room for Data Path 21 cell-sizing. MCMM mode DMSA ECO did better job than human in cell-sizing. PT_ECO consider DFFs as part of clock network, since the DFF/CK pin is the end point of the clock tree. PT_ECO cannot touch the clock path cells. So, DFF2 cell is not upsized by the PT tool. Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 15

16 Solution I with Clock Path ECO -- Upsizing DFFs Upsize the DFFs will benefit the setup fix in the following ways: DFF component delay # will improve. New upsized DFF improves the transition delay for downstream cells, which give possibility for another round of PT_ECO run to optimize the data path cells. So we plan to do: upsizing DFF + additional PT_ECO run Enhancement to fix_eco_timing to allow DFF sizing will be add into future PrimeTime release( ). Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 16

17 Solution II with Clock Path ECO -- Clock tree re-stitching Clock skew borrowing for left-over setup fix. 1 st level & 2 nd level(~10% chance) borrowing. By re-arrange the launch/capture clock to the same CTS branch, we can get the extra CRPR bonus for this in-depth study re-stitching. Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 17

18 2 nd Level Setup Margin Borrowing DFF3 DFF2 DFF Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 18

19 Extra bonus for CRPR with Clock Tree Re-stitching DFF 2 DFF 1 Re-stitching Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 19

20 Solution III with Clock Path ECO --- Clock tree in-law unit Utilize PD tool(icc or Encounter) to build the in-law ECO clock structure. Targeting insertion # is pre-calculated. May need two round of spef->eco to get the right insertion #. Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 20

21 Questions & Comments Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 21

22 THANKS Find EDA Tools for A Faster Timing Closure with ECO & Clock Path ECO 22