1. Power/Ground Network Aware and Row- Based Solutions to the Crosstalk Driven Routing Problem
Jinghong Liang,Tong Jing,
Xianlong Hong Jinjun Xiong, Lei He
CS&T Department EE Department
Tsinghua University UCLA
Beijing , China Los Angeles, CA, USA
Speaker: Jinghong Liang

2. Outline
1. Introduction
2. Our Work (Power/Ground Network Aware and Row- Based Algorithm)
3. Experimental Results & Discussions
4. Conclusions
November 23, 2018
Asicon2005,Shanghai,China

3. Coupling effects and crosstalk
Backgrounds
VLSI / ULSI
Coupling effects and crosstalk
System-On-a-Chip (SOC)
Clock frequency increases
New challenge to global routing
Global routing plays an important role in very/ultra large scale integrated circuits (VLSI/ULSI) physical design
The progress in VLSI/ULSI enables system-on-a-chip (SOC) integration instead of system-on-a-board (SOB) integration
Chip design is with greatly shrinking of geometries and giga-hertz clock frequencies
All these advances enable us to get high-performance chips
However, one of the great concerns is coupling effects and crosstalk
Crosstalk elimination has become a challenge to global routing
November 23, 2018
Asicon2005,Shanghai,China

4. The existing works can be divided into three categories
Previous Work (1)
The existing works can be divided into three categories
Noise modeling
Noise minimization
Simultaneous noise minimization and performance optimization .
November 23, 2018
Asicon2005,Shanghai,China

5. Previous Work (2)
Simultaneous noise minimization and performance optimization
[L. Zhang, T. Jing, X. L. Hong, J. Y. Xu, J. J. Xiong, L.He. ASICON, 2003]----(PO-GR)
[J. Y. Xu, X. L. Hong, T. Jing, L. Zhang, J. Gu. ASP-DAC, 2004]
[ T. Jing, L. Zhang, J. H. Liang, J. Y. Xu, X. L. Hong, J. J. Xiong, L. He. ASP-DAC, 2005, ]----(AT-PO-GR)
All proposed performance optimization global routing algorithms considering crosstalk reduction. The first mainly focuses on coupling capacitance and uses spacing method. The second considers coupling inductance and is based on shield insertion.The last obtain routing solutions with less routing area and greatly decrease running time.
[L. Zhang, T. Jing, X. L. Hong, J. Y. Xu, J. J. Xiong, L.He. ISCAS, 2004]----(T-PO-GR)
Presented an efficient RLC crosstalk reduction algorithm
November 23, 2018
Asicon2005,Shanghai,China

6. Outline
1. Introduction
2. Our Work (Power/Ground Network Aware and Row- Based Algorithm)
3. Experimental Results & Discussions
4. Conclusions
November 23, 2018
Asicon2005,Shanghai,China

7. Global Routing Graph (GRG) with P/G network
November 23, 2018
Asicon2005,Shanghai,China

8. Our Major Contribution
Goal: to meet the practical applications and reduce potential vias
The major contribution of this paper is a power/ground network aware and row-based solution to the crosstalk driven routing problem.
The proposed algorithm can achieve more than 72% on average improvements for the adjacent edges while considering power/ground network, which greatly reduces potential vias.
November 23, 2018
Asicon2005,Shanghai,China

9. Problem Formulation Let Then we have Minimize Subject to:
(1)
(2)
(3)
Formula(1) is the congestion constraint, which forbids the overflow on each GRG edge
Formula(2) guarantees the actual delay value from source i to sink j, T(i, j), is no more than the given timing constraint TD (i, j)
Formula(3) sets the upper bound of LSK, , for each source sink pair ij.
November 23, 2018
Asicon2005,Shanghai,China

10. LSK Model and Tabu Search
LSK Model for RLC Crosstalk Estimation Our crosstalk elimination is based on LSK model, which can be seen in [L. He and K. M. Lepak. ISPD, 2000]
Tabu Search
It is a famous algorithm and and be seen in many references.
November 23, 2018
Asicon2005,Shanghai,China

11. Incongruous Grid Problem
Since we assume that shields provided by P/G network are as long as three GRG edges, the previous routing results should be improved to meet the practical applications.
November 23, 2018
Asicon2005,Shanghai,China

12. Row-Based Solution The “dog-leg” problem.
Segments of the same net in adjacent GRG edges but are in different tracks (denoted by the order in the global routing phase), which makes more potential vias in detailed routing. Two segments of Net1 are not in the same track.
November 23, 2018
Asicon2005,Shanghai,China

13. Our Methods(1) 1. Obtain Row-Based Solution(1)
We still use Tabu search method to eliminate crosstalk noise.
The former cost formula of a GRG edge in AT-PO-GR is
cost(x) = w1 c1 + w2 c2 + w3 c3 + w4 c4
where w1, w2, w3, and w4 are the weights that equal to 13, 2, 13, and 10, respectively. c1 is the number of adjacency of sensitivity rate, c2 is the sum of violation Keff value, c3 is the number of Keff violation, and c4 is the number of shield inserted.
November 23, 2018
Asicon2005,Shanghai,China

14. 1. Obtain Row-Based Solution(2)
But we use a new cost formula as follows to take the “dog-leg” problem into consideration.
cost(x) = w1 c1 + w2 c2 + w3 c3 + w4 c4 + w5 c5
where c1,c2,c3,c4,w1,w2,w3 and w4 are the same as that of former cost formula, but we add w5 and c5 here. w5 equals 15, c5 = (1- a / b), a is the number of the adjacent segments of a net in the same tracks, b is the capacity of the GRG edge. So if a is bigger, the cost is smaller.
November 23, 2018
Asicon2005,Shanghai,China

15. Our Methods(2) 2. Tackle Incongruous Grid Problem(1)
In former algorithm like AT-PO-GR, we assumed that shields are as long as one GRG edges, which did not take actual P/G network into consideration.
Aware of P/G network, we assume that the horizontal shields are as long as 3 GRG edges. We try to make the 3 adjacent horizontal GRG edges have the same shield order by using the following method.
November 23, 2018
Asicon2005,Shanghai,China

16. 2. Tackle Incongruous Grid Problem(2)
Firstly, we partition all the horizontal GRG edges into edge groups, each of which includes 3 adjacent edges.
Then, in the same edge group, we can get the critical edge, which has the largest shield number. After that, we let the same shields track (i.e., the same shield order) in the other two edges (non-critical edges).
At last, we can adjust the segments in the non-critical edges to make use of the assigned shields.  
November 23, 2018
Asicon2005,Shanghai,China

17. Outline
1. Introduction
2. Our Work (Power/Ground Network Aware and Row- Based Algorithm)
3. Experimental Results & Discussions
4. Conclusions
November 23, 2018
Asicon2005,Shanghai,China

18. Experimental Environments
Platform
Hardware: sun V880 fire workstation
Software: gcc2.9.1, solaris5.8
Benchmark Data
Circuits
Number of nets
GRG grids C2
745
9*11 C5
1764
16*18 C7
2356
S13207
4953
24*26
AVQ
21581
65*67
Parameters Setting
LSK bound at each sink is set to be 1000
Na=350, Nb=20, Nc=10, and Tabu length=3
November 23, 2018
Asicon2005,Shanghai,China

19. In Comparison with Typical Algorithms
AT-PO-GR [t. Jing, L. Zhang, J. H. Liang]
Proposed performance optimization global routing algorithms considering crosstalk reduction. It obtain routing solutions with less routing area and running time.
RB denotes the algorithm to get a row-based solution. IG denoted the algorithm considering incongruous grid problem.
We will compare our RB and IG with the above algorithms focusing on area, running time, etc.
November 23, 2018
Asicon2005,Shanghai,China

20. COMPARSION OF NUMBER OF ADJACENT EDGES HAVE SAME TRACK POSITION
Circuits
AT-PO-GR RB IG C2
116
339
202 C5
361
413
654 C7
382
416
797
S13207
1382
2322
4770
Avq
3207
5793
12513
Aver imp
------
72.84%
159.85%
November 23, 2018
Asicon2005,Shanghai,China

21. COMPARSION OF TOTAL WIRE LENGTH
Circuits
AT-PO-GR RB IG C2
462204
465886 C5 C7
S13207
Avq
Aver imp
------
0.29%
November 23, 2018
Asicon2005,Shanghai,China

22. COMPARSION OF TOTAL RUNNING TIME
Circuits
AT-PO-GR RB IG C2
87.21
70.44
98.08 C5
257.93
212.20
275.13 C7
331.25
279.21
345.41
S13207
Avq
Aver imp
------
18.33%
-3.47%
November 23, 2018
Asicon2005,Shanghai,China

23. COMPARSION OF TOTAL AREA
Circuits
AT-PO-GR RB IG C2
168*204
174*203
175*203 C5
304*332
301*333
302*333 C7
342*365
360*377
364*377
S13207
1208*1410
1203*1420
1216*1420
Avq
1216*1001
1215*1003
1223*1003
Aver imp
------
-2.30%
-3.08%
November 23, 2018
Asicon2005,Shanghai,China

24. Outline
1. Introduction
2. Our Work (Power/Ground Network Aware and Row- Based Algorithm)
3. Experimental Results & Discussions
4. Conclusions
November 23, 2018
Asicon2005,Shanghai,China

25. Conclusions
A performance and RLC crosstalk driven routing algorithm considering P/G network and row-based solution is presented in this paper.
The experimental results show this algorithm can
take P/G network into consideration to meet the practical applications,
and can give a row-based routing solution to minimize potential vias, which is useful for good manufacturability.
November 23, 2018
Asicon2005,Shanghai,China

26. Future Work
As our future work, we plan to make our algorithm more practical to real chip routing, and design better strategies for crosstalk elimination.
November 23, 2018
Asicon2005,Shanghai,China

27. Thank you! Jinghong Liang(梁敬弘) Dept . of CST, Tsinghua Univ.
Beijing , P. R. China
Tel.:
Fax:
November 23, 2018
Asicon2005,Shanghai,China