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Performance Optimization Global Routing with RLC Crosstalk Constraints

Performance Optimization Global Routing with RLC Crosstalk Constraints. Ling Zhang, Tong Jing, Xianlong Hong, Jingyu Xu Jinjun Xiong, Lei He Dept. of CST, Tsinghua Univ Dept. of EE, UC, Los Angeles. Outline. Introduction Previous Work

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Performance Optimization Global Routing with RLC Crosstalk Constraints

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  1. Performance Optimization Global Routing with RLC Crosstalk Constraints Ling Zhang, Tong Jing, Xianlong Hong, Jingyu Xu Jinjun Xiong, Lei He Dept. of CST, Tsinghua Univ Dept. of EE, UC, Los Angeles

  2. Outline • Introduction • Previous Work • Our Algorithm: CEE-Gr • Experimental Results & Discussions • Conclusions ASICON2003, Beijing

  3. Introduction • Device size shrinking and clock frequency increasing • Coupling capacitance and inductance could not be ignored • Longer delay and crosstalk caused by coupling effects • Global routing with performance optimization becomes more important. ASICON2003, Beijing

  4. Outline • Introduction • Previous Work • Our Algorithm: CEE-Gr • Experimental Results & Discussions • Conclusions ASICON2003, Beijing

  5. Previous Work (1) • Noise minimization • Spacing in detailed routing (K. Chaudhary, A. Onozawa et al, 1993) • Track permutation in detailed routing (T. Gao, C. L. Liu, 1996) • Wire perturbation in detailed routing (P. Saxena, C. L. Liu, 1999) • Crosstalk reduction after global routing (T. X. Xue, E. S. Kuh, D. F. Wang, 1997) (J. J. Xiong, J. Chen, J. Ma, L. He, 2002) ASICON2003, Beijing

  6. Previous Work (2) • Noise modeling • Sakurai model (T. Sakurai, C. Kobayashi, M. Node, 1993) • LSK model for calculating coupling inductance (L. He, K. M. Lepak, 2000) • Model for calculating noise voltage (K. M. Lepak, I. Luwandi, L. He, 2001) ASICON2003, Beijing

  7. Outline • Introduction • Previous Work • Our Algorithm: CEE-Gr • Experimental Results & Discussions • Conclusions ASICON2003, Beijing

  8. Our Algorithm: CEE-Gr The major contribution of this work • We present a performance optimization global routing algorithm, named CEE-Gr, with RLC crosstalk constraints. • To our knowledge, it is the first to study RLC coupling noise, timing performance, and routability simultaneously at global routing level. ASICON2003, Beijing

  9. e GRC 1 GRG v v 1 2 Problem Formulation Fig.1 Global Routing Graph(GRG) ASICON2003, Beijing

  10. The CEE-Gr Algorithm (1) • Gr: Timing and congestion optimization • CEE: Crosstalk estimation and elimination • Gr firstly generates an initial routing solution considering congestion and timing optimization • Then, CEE eliminates the crosstalk from the solution by inserting shields and gets a mid-result • Finally, regard the mid-result as input and send it to Gr for iterations ASICON2003, Beijing

  11. Gr (without crosstalk consideration) CEE Gr (subtract tracks used by shields) The CEE-Gr Algorithm (2) generate initial routing solution considering congestion and timing optimization eliminates the crosstalk from the solution by inserting shields and gets a mid-result do iterate again regarding the mid-result as input Fig.2 CEE-Gr flow chart ASICON2003, Beijing

  12. (1) Gr • Congestion and timing optimization • Based on our previous methods • SSTT (search space traversing technology) and RINO (considering independent of net ordering) (T. Jing, X. L. Hong, H. Y. Bao, Y. C. Cai, J. Y. Xu, 2001) • Critical-network-based technology (T. Jing, X. L. Hong, H. Y. Bao, Y. C. Cai, J. Y. Xu et al, 2002) ASICON2003, Beijing

  13. (2) CEE (1) • Eliminate crosstalk in each GRG: According to each , this step applies simulated annealing method in each region to insert shields, so that all region’s crosstalk is within bound value. • Local Refinement: Check each net to eliminate possible remnant crosstalk and delete unnecessary shields to minimize the area. ASICON2003, Beijing

  14. Get global routing solution from Gr and Crosstalk bound budgeting Eliminate crosstalk in each region Local refinement CEE (2) CEE (2) partition the LSK bound at each sink of a net into the GRG edges belonging to the source-sink paths. • Flow chart: LSK bound Insert shield with simulated annealing method Check each net to eliminate possible remnant crosstalk and delete unnecessary shields to minimize total area. ASICON2003, Beijing

  15. Crosstalk Bound Budgeting (1) • CBUD (uniform distributed crosstalk budgeting) strategy (1) The crosstalk bound at sink pijfor net Ni Crosstalk sub-bound assigned to each GRG region t len The total length from the source pioto sink pij ASICON2003, Beijing

  16. Crosstalk Bound Budgeting (2) • CBLP (linear programmed crosstalk budgeting) strategy Consider different congestion situation in different GRG region in partitioning. Thus, introduce a linear programming problem. The objective is to minimize the number of used tracks in most congested GRG region. ASICON2003, Beijing

  17. …… R1 R2 Rt CBLP (1) • One dimensional GRG--horizontal wires routing in one row: Fig.4 One dimensional GRG ASICON2003, Beijing

  18. CBLP (2) Minimize Subject to (2) (3) (4) ht: Number of tracks used by nets, shields or obstacles in region Rt Gt: Number of nets in region Rt Ot: Number of obstacles in region Rt : Estimated number of shields in region Rt ASICON2003, Beijing

  19. …… …… …… …… CLMSET ROWSET CBLP (3) • Two dimensional GRG: Fig.5 Two dimensionsal GRG ASICON2003, Beijing

  20. CBLP (4) Minimize Subject to (5) (6) (7) (8) ASICON2003, Beijing

  21. Outline • Introduction • Previous Work • Our Algorithm: CEE-Gr • Experimental Results & Discussions • Conclusions ASICON2003, Beijing

  22. Experimental Results (1) Technology: 0.2um Sensitivity rate: 0.5 for all nets and sensitivity matrix is random. LSK bound:1000 at each sink ASICON2003, Beijing

  23. Experimental Results (2) COMPARISON BETWEEN Gr AND CEE-Gr WITH CBUD ASICON2003, Beijing

  24. Experimental Results (3) COMPARISON BETWEEN CBUD AND CBLP IN CEE-Gr ASICON2003, Beijing

  25. Discussions • CEE-Gr can eliminate all crosstalk by adding shields, while the initial solution has serious crosstalk. • The increase in wire length of CEE-Gr is quite small compared to Gr. • The minimum redundancy of delay (requiredDelay-currentDelay) is almost unaffected. • CBUD strategy consumes less shields and small area than CBLP strategy. • CBLP reduces the maximal used tracks in GRG, which is helpful for optimization with other constraints and low power design. • Simulated annealing method increases the running time of CEE-Gr.(40 mins for C2) ASICON2003, Beijing

  26. Outline • Introduction • Previous Work • Our Algorithm: CEE-Gr • Experimental Results & Discussions • Conclusions ASICON2003, Beijing

  27. Conclusions • Tackle coupling noise, timing performance and routability simultaneously • Take coupling inductance into consideration • Obtain good routing results • Efficiently eliminate crosstalk throughout the global routing phase by inserting shields and has little influence on wire length and timing performance. ASICON2003, Beijing

  28. THANK YOU Ling Zhang Dept. of CST, Tsinghua Univ Email: zhangling@tsinghua.org.cn ASICON2003, Beijing

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