IBM Corp. What Makes A Design Difficult to Route Charles J. Alpert, Zhuo Li, Michael Moffitt, Gi-Joon Nam, Jarrod Roy, Gustavo Tellez
What Makes a Design Difficult to Route What Does This Man and a Router Have in Common? Young math whiz Discovers computer programming Drops out of Harvard Starts Microsoft Works really hard Becomes very rich March 15, 2010 2 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Bill’s Opportunities ASR-33 Teletype 1968: 8 th grade March 15, 2010 3 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Some Math Whiz, Computer Programmer, Hard Working Guys Bill Joy Scott McNealy Nov. 1954 Nov. 1954 Bill Gates Steve Jobs Oct. 1955 Feb. 1955 Eric Schmidt Apr. 1955 March 15, 2010 4 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route What’s the Difference Between These Guys? March 15, 2010 5 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route What Does a Router Have in Common with Bill Gates? Give them the opportunity to succeed, and they will Take away the opportunity to succeed, and they won’t March 15, 2010 6 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Routing is From Venus, Congestion Analysis is From Mars Floorplanning Floorplanning Placement Placement Timing Closure Timing Closure Routing Congestion Analysis March 15, 2010 7 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Measuring Routing Quality (40-track per gcell) March 15, 2010 8 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Routable gcell (75% full) March 15, 2010 9 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Unroutable gcell (150% full) – 20 Nets of Overflow March 15, 2010 10 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Example Congestion Map Vertical Congestion Horizontal Congestion March 15, 2010 11 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Congestion Map with Better Physical Synthesis Vertical Congestion Horizontal Congestion March 15, 2010 12 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Common Routing Metrics Number of Overflow Nets = Number of Nets Over 100% Congested Number of nets over 90% congested Number of nets over 80% congested Average congestion of 20% worst gcells March 15, 2010 13 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Handling Routing Blockages March 15, 2010 14 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route 50% Full or 95% Full? March 15, 2010 15 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route The Wire Stack 32nm 65nm 250nm 130nm 90nm 45nm March 15, 2010 16 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Resistance per mm 6 5 65 nm 45 nm 4 32 nm 3 2 1 0 thin medium thick March 15, 2010 17 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Routing Tracks on 4X Metal March 15, 2010 18 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Only 2 Tracks Left, but Not Congested March 15, 2010 19 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Routing Tracks on 10X Metal March 15, 2010 20 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Routing Tracks on 16X Metal March 15, 2010 21 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Is This Net Congested? Different routers can and will report different routing metrics for the same exact global routes! March 15, 2010 22 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Cross section of a gcell 4x 2x 1x March 15, 2010 23 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Timing Closure Constrains The Router Layer assignment / wire sizing assigns constraints for the router March 15, 2010 24 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Is This a Congestion Problem? 4x 2x 1x March 15, 2010 25 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Is It Routable? Avg 20% = 89.1 Avg 20% = 83.5 #nets > 100% = 9532 #nets > 100% = 532 #nets > 90% = 25785 #nets > 90% = 2785 Avg 20% = 81.7 Avg 20% = 78.2 #nets > 100% = 3942 #nets > 100% = 16 #nets > 90% = 11880 #nets > 90% = 753 March 15, 2010 26 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Congestion Analysis Versus Routing Congestion Analysis Probabilistic Route Fast Route Carefully No A Little Completely Completely Scenic Scenic Scenic Scenic Over Around Around Blockages Blockages Blockages Obey layer May violate layer May violate layer constraints constraints constraints March 15, 2010 27 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Minimizing Wire Generally Improves Congestion Bad placement Good placement March 15, 2010 28 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Spread it Uniformly Doesn’t Always Work March 15, 2010 29 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route CRISP Progression Horizontal Congestion Vertical Congestion Initial Iteration 5 Iteration 10 Iteration 15 Placement March 15, 2010 30 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Effect of Timing Driven-Placement Initial placement Timing-driven placement March 15, 2010 31 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Effect of Timing Driven-Placement Initial placement Timing-driven placement March 15, 2010 32 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Impact of More Efficient Area Usage Avg 20%: 108.06 Avg 20%: 86.89 >90% nets: 37855 >90% nets: 7307 >100% nets: 21364 >100% nets: 1147 March 15, 2010 33 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route “Sitting” in the Student Section Routing difficulty Density March 15, 2010 34 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Buffering Along A Global Route March 15, 2010 35 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Buffer Packing March 15, 2010 36 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Blockage Avoidance Routing March 15, 2010 37 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route The Corona Effect March 15, 2010 38 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Corona Effect + Too Much Thick Metal March 15, 2010 39 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route Hot Spots versus Opens and Shorts March 15, 2010 40 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route What Makes a Design Difficult to Route? Bad floorplan Over packing dense logic Inefficient area minimization Over weighting for timing-driven placement Buffering too packed Over-constraining router Not capturing local routing isses Even if successful, don’t mess up timing too much March 15, 2010 41 2010 International Symposium on Physical Design
What Makes a Design Difficult to Route What Does a Child Have in Common with a Router ? We want to create opportunities to succeed. Just because opportunity is provided, they may not take advantage. We don’t really know what the best opportunities are. March 15, 2010 42 2010 International Symposium on Physical Design
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