This document provides an overview of floorplanning in chip design. Floorplanning involves block placement, pin assignment, design partitioning, and other tasks. It aims to optimize chip area, wirelength, timing, and routability. Representations like sequence pairs and algorithms like simulated annealing are used. Floorplanning is important for estimating metrics early in design and improving subsequent steps like routing. It can eliminate guesswork and risks from hierarchical flows.

1. FLOOR PLANNING
BY AMIT KR. CHAMOLI

2. Outlines
 Introduction
 Efficacy
 Merits
 Input/Output
 Floorplanning Problem
 Challenges
 Floorplanning Representations and Approaches
 Floorplanning Model
 Algorithms
 Assignment
 Conclusion

3. Introduction
 Floorplanning is an essential element of
hierarchical design flows, especially for
large SoC(System On Chip) designs. A
typical SoC could include hundreds of
RAMs, soft and hard IP(Intellectual
property), analog blocks, and multiple
power domains.
 A hierarchical methodology that extends
the capacity of design-automation tools,
improves tool runtimes, and mitigates
overall design risk by minimizing last
minute design changes

4. Floorplanning
 block placement
 Pin assignment
 Design partitioning
 Time budgeting
 Power and clock planning

5. Efficacy
 Floorplanning is considered when the
Design has not met timing or does
not meet timing consistently
 Critical logic to Improve performance
 Reduce routing congestion
 Improve module-level performance
and Area
 Improve Implementation Run time
and consistency with partitions

6. Merits
 Eliminate Guess work
 Minimize the impact of surprises in
chip assembly
 Reduce the risks associated with
Hierarchical Flows and Shorten the
time to design closure
 Timing
 Congestion
 More Flexibility in Design layout

7. Floorplanning phase
 Input
A set of blocks with constraints on area,
shapes, relative positions, Constraints on
chip area and aspect ratio, Netlist.
 Output
Shapes, Locations, Pin positions of the
blocks
 Objective Functions
Performance, chip area, and wire length

8. Floorplanning Problem
The floorplanning problem is to plan the
positions and shapes of the modules at the
beginning of the design cycle to optimize
the circuit performance:
 chip area
 total wirelength
 delay of critical path
 routability
 others, e.g., noise, heat dissipation, etc.

9. Floorplanning Challenges
 Bad Input/output Pad and Macro
placement
 Inaccurate Timing ,Area and Power
estimation
 Inadequate Region shaping ,
Partitioning and Pin Assignment

10. Floorplanning strategies
 Floorplanning must take into account
blocks of varying function, size,
shape.
 Must design:
 space allocation
 signal routing
 power supply routing
 clock distribution

11. Purposes of Floorplanning
 Early in design:
 Prepare a floorplan to budget area, wire
area/delay.Tradeoffs between blocks can
be negotiated.
 Late in design:
 Make sure the pieces fit together as
planned.
 Implement the global layout.

12. Floorplanning: Why Important?
 Early stage of physical design
 Determines the location of large blocks
 detailed placement easier (divide and
conquer!)
 Estimates of area, delay, power
 important design decisions
 Impact on subsequent design steps
(e.g., routing, heat dissipation analysis
and optimization)

13. Floorplanning tips
• Develop a wiring plan. Think about how
layers will be used to distribute important
wires.
• Sweep small components into larger blocks.
A floorplan with a single NAND gate in the
middle will be hard to work with.
• Design wiring that looks simple. If it looks
complicated, it is complicated.
• Draw separate wiring plans for power and
clocking. These are important design tasks
which should be tackled early.

14. Representations and Approaches
 Two popular approaches to floorplan
1. Simulated annealing
2. Analytical formulation
 Floorplan representations
1. Normalized Polish expression
2. B*-tree
3. Sequence Pair
4. Polar Graph

15. Floorplanning Model
1. Slicing floorplans
2. Non-slicing floorplans
 Slicing Tree
 A binary tree that models a slicing
structure.
 Each node represents a vertical cut line
(V), or a horizontal cut line (H).
 A third kind of node called Wheel (W)
appears for non sliceable floorplans

16. Floorplanning Model (Cont)
A Non-Slicing FloorplanSlicing Floorplan and its Slicing Tree

17. Floorplanning Algorithms
 Components
 “Placeholder” representation
 Usually in the form of a tree
 Slicing class: Polish expression
 Non-slicing class: O-tree, Sequence Pair, etc.
 Just defines the relative position of modules
 Perturbation
 Going from one floorplan to another
 Usually done using Simulated Annealing
 Floorplan sizing
 Choose the best shape for each module to minimize area
 Slicing: polynomial, bottom-up algorithm
 Non-slicing: Use mathematical programming (exact solution)
 Cost function
 Area, wire-length, ...

18. Classification of Algorithms
 Simulated Annealing
 Constraint Based methods
 (Integer) Linear Programming
Methods
 Rectangular Dualization Based
Methods
 Hierarchical Tree Based Methods
 Timing Driven Floorplanning
Algorithms

19. Simulated Annealing
 In this process, a material is first heated up
to a temperature that allow all its
molecules to move freely around and is
then cooled down very slowly.
 Perform computation that analogous to
physical process.
 The energy corresponds to the cost function
 Molecular movement corresponds to a sequence
of moves in the set of feasible solution
 Temperature corresponds to a control parameter
T which control the acceptance probability for a
move i.e. A good move

20. Wong-Liu Floorplanning Algorithm
 Uses simulated annealing
 Normalized Polish expressions represent
floorplans
 Cost function:
 cost = area + total WireLength
 Floorplan sizing is used to determine area
 After floorplan sizing, the exact location of each
module is known, hence wire-length can be
calculated

21. Wong-Liu Floorplanning Algorithm
(cont.)
 Moves:
 OP1: Exchange two operands that have
no other operands in between
 OP2: Complement a series of operators
between two operands
 OP3: Exchange adjacent operand and operator if the
resulting expression still a normalized Polish exp.
OP1OP1OP1OP1
OP1OP1OP1OP1 OP1OP1OP1OP1
12 | 4 – 3 | 12 | 3 – 4 | 12 - 3 – 4 | 12 - 3 4 - |

22. Assignment
 What are timing failure?
 What are the critical hierarchical
Block and Risk?
 Are changes/moves to the Floorplan
or critical logic going to be sufficient
to meet timing?
 Does anything else need to be
Floorplaned?

23. Conclusion
 Floorplanning is the foundation of a quality
IC implementation. The decisions made
regarding IO pad placement, macro
placement, partitioning, pin assignment,
and power planning ripple through the
place-and-route flow. Designers need
solutions that can handle extremely large
data sets, design variability and
complexity, in addition to enabling fast,
high-quality floorplanning.

24. Q & A
 THANK YOU