2010 International Symposium on Physical Design. March 15, 2010. What Does ... Design. March 15, 2010. Unroutable gcell (150% full) â 20 Nets of Overflow ...
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 2
2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Bill’s Opportunities ASR-33 Teletype
1968: 8th grade 3
2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Some Math Whiz, Computer Programmer, Hard Working Guys
Bill Gates Oct. 1955
Bill Joy Nov. 1954 Steve Jobs Feb. 1955
Scott McNealy Nov. 1954
Eric Schmidt Apr. 1955
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
What’s the Difference Between These Guys?
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2010 International Symposium on Physical Design
March 15, 2010
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 6
2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Routing is From Venus, Congestion Analysis is From Mars Floorplanning Placement Timing Closure
Floorplanning Placement Timing Closure Routing Congestion Analysis
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Measuring Routing Quality (40-track per gcell)
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Routable gcell (75% full)
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Unroutable gcell (150% full) – 20 Nets of Overflow
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Example Congestion Map Horizontal Congestion
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2010 International Symposium on Physical Design
Vertical Congestion
March 15, 2010
What Makes a Design Difficult to Route
Congestion Map with Better Physical Synthesis Horizontal Congestion
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2010 International Symposium on Physical Design
Vertical Congestion
March 15, 2010
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
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2010 International Symposium on Physical Design
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What Makes a Design Difficult to Route
Handling Routing Blockages
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
50% Full or 95% Full?
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
The Wire Stack
250nm 16
130nm
90nm
65nm
2010 International Symposium on Physical Design
32nm 45nm March 15, 2010
What Makes a Design Difficult to Route
Resistance per mm 6 5
65 nm 45 nm 32 nm
4 3 2 1 0 thin 17
medium
2010 International Symposium on Physical Design
thick March 15, 2010
What Makes a Design Difficult to Route
Routing Tracks on 4X Metal
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Only 2 Tracks Left, but Not Congested
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Routing Tracks on 10X Metal
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2010 International Symposium on Physical Design
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What Makes a Design Difficult to Route
Routing Tracks on 16X Metal
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2010 International Symposium on Physical Design
March 15, 2010
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! 22
2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Cross section of a gcell
4x
2x 1x 23
2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Timing Closure Constrains The Router
Layer assignment / wire sizing assigns constraints for the router 24
2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Is This a Congestion Problem?
4x
2x 1x 25
2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Is It Routable?
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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
2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Congestion Analysis Versus Routing
Congestion Analysis Probabilistic No Scenic
A Little Scenic
Over Blockages Obey layer constraints 27
Route Fast Completely Scenic Around Blockages May violate layer constraints
2010 International Symposium on Physical Design
Route Carefully Completely Scenic Around Blockages May violate layer constraints March 15, 2010
What Makes a Design Difficult to Route
Minimizing Wire Generally Improves Congestion Bad placement
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2010 International Symposium on Physical Design
Good placement
March 15, 2010
What Makes a Design Difficult to Route
Spread it Uniformly Doesn’t Always Work
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
CRISP Progression
Horizontal Congestion
Vertical Congestion
Initial Placement 30
Iteration 5
2010 International Symposium on Physical Design
Iteration 10
Iteration 15 March 15, 2010
What Makes a Design Difficult to Route
Effect of Timing Driven-Placement Initial placement
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2010 International Symposium on Physical Design
Timing-driven placement
March 15, 2010
What Makes a Design Difficult to Route
Effect of Timing Driven-Placement Initial placement
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2010 International Symposium on Physical Design
Timing-driven placement
March 15, 2010
What Makes a Design Difficult to Route
Impact of More Efficient Area Usage
Avg 20%: 108.06 >90% nets: 37855 >100% nets: 21364
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2010 International Symposium on Physical Design
Avg 20%: 86.89 >90% nets: 7307 >100% nets: 1147 March 15, 2010
What Makes a Design Difficult to Route
Routing difficulty
“Sitting” in the Student Section
Density 34
2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Buffering Along A Global Route
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Buffer Packing
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Blockage Avoidance Routing
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
The Corona Effect
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Corona Effect + Too Much Thick Metal
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2010 International Symposium on Physical Design
March 15, 2010
What Makes a Design Difficult to Route
Hot Spots versus Opens and Shorts
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2010 International Symposium on Physical Design
March 15, 2010
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
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2010 International Symposium on Physical Design
March 15, 2010
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. 42
2010 International Symposium on Physical Design
March 15, 2010
