687Lec19_Interconnect.pdf

687Lec19_Interconnect.pdf - ECEN 687 VLSI Design Automation...

Info icon This preview shows pages 1–16. Sign up to view the full content.

View Full Document Right Arrow Icon
ECEN 687 Lecture 19 1 ECEN 687 VLSI Design Automation Lecture 19 Interconnect Optimization
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2 R Buffers Reduce Wire Delay x/2 cx/4 cx/4 rx/2 t_unbuf = R( cx + C ) + rx( cx/2 + C ) t_buf = 2R( cx/2 + C ) + rx( cx/4 + C ) + t b t_buf – t_unbuf = RC + t b – rcx 2 /4 x/2 cx/4 cx/4 rx/2 C C R x t ECEN 687 Lecture 19
Image of page 2
3 Buffers Improve Slack RAT = 300 Delay = 350 Slack = -50 RAT = 700 Delay = 600 Slack = 100 RAT = 300 Delay = 250 Slack = 50 RAT = 700 Delay = 400 Slack = 300 Slack min = -50 Slack min = 50 Decouple capacitive load from critical path RAT = Required Arrival time Slack = RAT - Delay ECEN 687 Lecture 19
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
4 Problem Formulation Given n A Steiner tree n RAT at each sink n A buffer type n RC parameters n Candidate buffer locations Find buffer insertion solution such that the slack min is maximized ECEN 687 Lecture 19
Image of page 4
5 Candidate Buffering Solutions ECEN 687 Lecture 19
Image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
6 Candidate Solution Characteristics Each candidate solution is associated with n v i : a node n c i : downstream capacitance n q i : RAT v i is a sink c i is sink capacitance v is an internal node ECEN 687 Lecture 19
Image of page 6
7 Van Ginneken s Algorithm •Start from sinks •Candidate solutions are generated Candidate solutions are propagated toward the source ECEN 687 Lecture 19
Image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
8 Solution Propagation: Add Wire c 2 = c 1 + cx q 2 = q 1 – rcx 2 /2 – rxc 1 r: wire resistance per unit length c: wire capacitance per unit length (v 1 , c 1 , q 1 ) (v 2 , c 2 , q 2 ) x ECEN 687 Lecture 19
Image of page 8
9 Solution Propagation: Insert Buffer n c 1b = C b n q 1b = q 1 – R b c 1 – t b n C b : buffer input capacitance n R b : buffer output resistance n t b : buffer intrinsic delay (v 1 , c 1 , q 1 ) (v 1 , c 1b , q 1b ) ECEN 687 Lecture 19
Image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
10 Solution Propagation: Merge c merge = c l + c r q merge = min(q l , q r ) (v, c l , q l ) (v, c r , q r ) ECEN 687 Lecture 19
Image of page 10
11 Solution Propagation: Add Driver n q 0d = q 0 – R d c 0 = Slack min n R d : driver resistance n Pick solution with max Slack min (v 0 , c 0 , q 0 ) (v 0 , c 0d , q 0d ) ECEN 687 Lecture 19
Image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
12 Example of Solution Propagation (v 1 , 1, 20) 2 2 v 1 v 1 (v 2 , 3, 16) r = 1, c = 1 R b = 1, C b = 1, t b = 1 R d = 1 (v 2 , 1, 12) v 1 (v 3 , 5, 8) v 1 (v 3 , 3, 8) slack = 5 slack = 3 Add wire Add wire Insert buffer Add wire Add driver Add driver ECEN 687 Lecture 19
Image of page 12
13 Example of Merging Left candid ates Right candidates Merged candidates ECEN 687 Lecture 19
Image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
14 Solution Pruning Two candidate solutions n (v, c 1 , q 1 ) n (v, c 2 , q 2 ) Solution 1 is inferior if n c 1 > c 2 : larger load n and q 1 < q 2 : tighter timing ECEN 687 Lecture 19
Image of page 14
15 Pruning When Insert Buffer They have the same load cap C b , only the one with max q is kept ECEN 687 Lecture 19
Image of page 15

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 16
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern