From one switch to a hundred billion

We've climbed from electrons to transistors to logic gates. The last leap is from logic gates to a working processor — and it's a big one. A modern CPU is a city of nearly 100 billion transistors, all etched simultaneously onto a sliver of silicon a few hundred square millimeters in size.

Key Concept

Integrated Circuit (IC)

A complete electronic circuit — transistors, resistors, capacitors, and the wires connecting them — fabricated together on a single piece of semiconductor. Invented by Jack Kilby and Robert Noyce in 1958–59. Every chip you've ever touched is an IC.

Key Concept

Processor (CPU/GPU)

A specialized integrated circuit that fetches instructions, decodes them, and executes them by routing data through arithmetic and logic units. Built from millions of logic gates organized into pipelines, caches, and execution units.

Key Concept

Clock Speed (GHz)

The frequency at which a chip's logic synchronously updates. 3 GHz = 3 × 10⁹ cycles per second. Faster clock = more operations per second, but also more dynamic power and more heat.

Key Concept

Transistor Density

Transistors per square millimeter of die area. Apple's M2 packs ~150 million transistors per mm². Higher density = more compute and memory in the same area = faster, cheaper, more power-efficient chips.

Key Concept

Fabrication Node (nm)

The naming convention for a process generation: '3nm', '5nm', '7nm'. Originally referred to the gate length in nanometers; today it is mostly a marketing label — actual smallest features are larger, but each new node still roughly doubles density.

Diagram · Zoom from package to single transistor

interactive

Chip Package · ~40 mm

The black square you see on a motherboard.

~40 mm~10 mm~100 µm~100 nm~3 nm

Watch the auto-zoom step through the five orders of magnitude that separate a chip you can hold in your hand from a single transistor.

Photolithography in one paragraph. A wafer is coated with a light-sensitive polymer, then UV light shines through a mask carrying the chip's pattern, exposing only the regions you want to keep (or remove). Chemical etches and material depositions repeat this dance hundreds of times — each layer transferring a different sub-pattern. After ~600 process steps and 3 months in a fab, a single 300 mm wafer yields hundreds of finished chips.

'3 nm' isn't really 3 nm. A modern '3 nm' node has gate lengths around 12 – 16 nm and metal pitches around 22 – 24 nm. The 'X nm' label is shorthand for generation, not a measurement — but density per mm² still doubles roughly every node, which is what matters.

Checkpoint · +5 XP

Which level is the smallest in the hierarchy?

Try It Yourself

Stack up a real chip

Open the Chip Builder. Drag in a few NAND gates and an SRAM cell. Use the Stack Up button to wire them into a small functional block — and watch how quickly transistor counts climb.

Open Chip Builder

Lesson Summary

Hierarchy: transistors → logic gates → functional blocks → processor.
Modern chips contain tens of billions of transistors, all manufactured in parallel by photolithography.
Clock speed (GHz) sets how many switching cycles per second the chip performs.
'3nm node' is a marketing label — the real feature sizes are larger, but density per mm² still doubles roughly every node.

Test Your Knowledge · +50 XP

Order from smallest to largest:

Clock speed of 3 GHz means:

What does 'fabrication node' refer to?

Higher transistor density usually leads to:

Which is true about modern '3 nm' chips?