What is Frontend in the World of Chips?

In the previous post, we understood what RTL is and how you “write” hardware. Now we’ll understand where RTL fits in the big picture - and what exactly Frontend is.

What is Frontend?

In the chip world, Frontend is the stage where you design the logical behavior of the chip.

This is the stage where:

• You define what the chip needs to do
• You write the RTL
• You verify the behavior is correct
• You ensure everything works before starting to build anything physical

Frontend is the theoretical design - the work that happens before there’s a single transistor.

What Actually Happens in Frontend?

1. Specification Definition

What does the chip need to do? What interfaces will it have? What are the required performance metrics?

This is where requirements are understood.

2. Architecture Design

Deciding which blocks will be in the chip:

• Computing units
• Memories
• Controllers
• Communication buses

And how they’ll communicate with each other.

3. Writing RTL

Here, hardware engineers write the logical description in languages like Verilog or SystemVerilog.

Each module is described precisely:

• What are the inputs and outputs
• How it responds to the clock
• What’s the internal logic

4. Verification

This is the largest part of Frontend.

Here, the RTL is tested:

• Does it do what it should?
• Does it behave correctly in every scenario?
• Are there any bugs?

Using:

• Simulations
• Testbenches
• UVM (Universal Verification Methodology)
• Coverage analysis

70% of Frontend work is Verification.

Why is Frontend So Important?

Because at this stage, errors can still be fixed easily.

Error in RTL? → Change a line → Run simulation again → Works.

Error after manufacturing? → Millions of dollars → Months of delay → New Tapeout.

Frontend is where you prevent problems.

What’s the Difference Between Frontend and Backend?

Frontend	Backend
Logical design	Physical design
RTL, simulations, Verification	Synthesis, Place & Route, Timing
What the chip does	How the chip is built
Behavior	Transistors, wires, layers
Tools: Verilog, UVM, simulators	Tools: Synthesis, STA, Layout

Frontend deals with what. Backend deals with how.

An Analogy to Clear Things Up

Frontend is like designing a building:

• What will the building contain? (Stores, apartments, offices)
• How many floors?
• Where are the elevators?
• How will people move around?
• Does the design make sense?

Backend is actually building the building:

• Placing columns
• Connecting rebar
• Pouring concrete
• Checking the structure stands

Frontend = architectural plan. Backend = physical construction.

Main Tools in Frontend

• Verilog / SystemVerilog - RTL writing languages
• Simulators (VCS, ModelSim, Xcelium) - to run and test the RTL
• UVM - methodology for building tests
• Coverage tools - to measure how much of the system was tested
• Formal verification - mathematical proofs that logic is correct

Summary

Frontend is:

• The stage where you design the logical behavior of the chip
• Includes architecture, RTL, and Verification
• Where most bugs are found and caught
• The foundation for everything that comes next in Backend

Without good Frontend - there’s no good chip.

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In the next post, we’ll dive deeper into RTL itself - what is Verilog, what does RTL code look like, and why it’s completely different from regular programming languages.