Introduction
Macros - pre-designed, reusable circuit blocks/components.
memory, I/O cells, or complex logic blocks.
used to simplify the design process, reduce design time and enhance the overall efficiency of integrated circuits (ICs).
Why Macros are Important in VLSI ? 
Design Reusability – saves time
Optimization – optimised for PPA ( power, performance, area )
Faster Time-to-Market - speeds up the design process
Complexity Management - instead of dealing with individual transistors
Macro Placement
process of determining the optimal positions of large functional blocks (macros) within the chip layout during the physical design phase of an integrated circuit (IC).
Why Macro Placement ? 
Minimizes wire lengths
Optimizes chip area
Improves signal integrity(noise)
Facilitates easier routing (reduce congestion)
Ensures the design meets timing, area, power,
Types of Macro Placement
1. Command Method/tool command method : - not accurate
2. Manual method : - used in industry
3. Machine learning macro placement : - runtime is too long
Tools for Macro Placement
Cadence Innovus :
Synopsys IC Compiler :
Mentor Graphics Tools :
These tools leverage advanced algorithms to automate and optimize the placement process
Macro Placement Guidelines
These are the set of principles and best practices used in the VLSI design process to ensure the efficient and effective positioning of macros inside the core area.
1. Group/ Place macros based on hierarchies
- different colour can be given to sub families.
2. Place macros from core edges –
- to prevent from congestion (shortage of tracks)
3. Place Macros based on flylines –
-imaginary lines –connection between ports ¯os
Data flow - macros & port
Net Connection – macro to macro
4. Don’t stack macros near the port.
-It might increase congestion.
5. Leave sufficient space between macros
- min. spacing –at least 1 VDD & 1 VSS strap has to run.
6. Avoid Criss cross connections : - to minimize the wire length.
7. Apply soft/partial/hard/routing blockage in macro channel
- hard – no std cell & routing cannot be done
- partial – blocked 60 percent means, can put 40pc std cells
- soft- only inverters and buffers
- routing blockage – specify routing of metal layers
8. Apply keep-out margin / halo around macro
- to protect macro pins (no DRC violations)
- to avoid congestion near macro pins
Benefits of Effective Macro Placement
Improved Performance: Shorter wire lengths, reduced delays.
Optimized Area: Better area utilization, reducing chip size.
Lower Power: Reduced power consumption through optimal routing and placement.
Conclusion
Macro placement is a crucial step in VLSI design.
Effective placement leads to better performance, reduced power consumption, and more efficient chip designs.
Advanced algorithms and tools help automate and optimize the placement process.