Placement - Physical Design - Part 2 - General Setup

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Dear Reader,

In our previous vlogs, we looked into the fundamentals of placement flow and algorithms. Here is the link to access Part 1 of the placement vlogs: Understanding of Placement Physical.

Before we discuss on a detailed exploration of placement algorithms, let's first address the setup requirements for the placement run. There are various setup and flow optimization settings available with EDA tools to explore, but let's focus on a few essential and mandatory setup requirements for the placement run.


1.Multiple Corner Optimization Setup:

In today's design practices, it's crucial to account for multiple corners and assess timing in various scenarios. Therefore, it is imperative to optimize your design for multiple corners during the placement run. We should aim to optimize our design for all available setup corners while possibly excluding the hold corner.

set_scenario_status <corner_for_setup> -active true


2. Physical Synthesis Netlist Setting:

If you are utilizing a physical synthesis netlist for the placement run, you can bypass the initial coarse placement stage. Enable the necessary variables to ensure that the tool skips these optional stages.



3.Spare Cell Placement:
Ensure that the spare cell placement variable is activated so that the tool adds spare cells at regular intervals to facilitate eco cycles.


4.Remove Unwanted Ideal Network:
Eliminate unwanted ideal networks before the placement run to prevent buffering of high fanout nets.

remove_ideal_network -all


5.Restricting Library Cell Usages:
Depending on the requirements, control the usage of library cells for timing and power optimization. Provide a list of cells not to be used and regulate the usage of high VT and low VT cells.


6.Pre-route Power Optimization:
Control which power optimization should be performed for specific scenarios.

Dynamic power optimization requires a switching activity file. You can read the SAIF file for the switching activity file, which provides toggle rates and static probabilities of nets.


These setups are fundamental requirements that need to be addressed. There are additional compulsory setups to be completed prior to placement.

    1. 1. Congestion Driven Setup
    2. 2. Timing Driven Setup

  1. We will look into these two critical setups in our next vlogs.

    Happy Learning.


Comments

  1. krishApril 30, 2024 at 12:33 PM

    what are the ideal networks here, if we wanted to prevent just buffering on that, why can't we make it don't_touch

    ReplyDelete

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