HOW COMPUTE WORKSBy Michael Hsu

GPU package

What does a GPU package substrate do?

Bare silicon needs a way to connect to a larger system. The package substrate supports the assembly and routes connections toward the circuit board. It belongs beneath the chips because it bridges their compact assembly and the board that carries the system. The model groups several routing layers for clarity; a substrate and a fine-pitch interposer are not the same component.

Explore it in the 3D GPU model

What it does

The substrate supports the package and routes electrical connections toward the circuit board. It gives the smaller chips a practical connection to the larger system.

Why it sits where it does

It forms the bottom of the package, beneath the interposer. In this model, solder contacts underneath connect the package to a board.

Connections inside a multi-chip package operate at a different physical scale from the connections on the system board. Packaging bridges those scales.

How it works

Multiple layers carry connections through the package. The interposer handles fine connections near the chips; the substrate carries connections toward the board. They have different jobs.

Limits and trade-offs

The substrate must fit many connections into a small area while supporting the assembly.

More chips and connections require increasingly complex routing and reliable assembly.

In Blackwell Ultra and MI300X

NVIDIA Blackwell Ultra and AMD MI300X

The organic substrate distributes power and ground, supports the assembly and fans signals out to the board. Nearby decoupling capacitors help stabilize voltage during load changes.

How it is made

  1. Build an insulating base with several layers of conductive connections.
  2. Add the contacts needed to join it to the rest of the package and board.
  3. Assemble and test the finished package.

How it developed

  1. From chips to systems

    Packaging becomes part of the architecture

    Advanced packages combine logic and memory through multiple connection layers. Their arrangement affects how an entire system can be built.

    SK hynix · How wafer-level packages are made ↗
  2. Early 2010s

    A bridge from assembled chips to a package

    TSMC described bonding chips to a wafer and attaching the resulting chip assembly to a substrate. This illustrates the substrate’s separate role underneath the chip assembly.

    TSMC · CoWoS test vehicle announcement ↗

Where it is used

Key terms

Substrate
The supporting base that carries connections through a package.

Sources

The 3D models are illustrative teaching schematics, not manufacturer CAD. Counts and layouts are simplified where the sources say so.

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