Examples of a computer system packaged in a three-dimensional stack of dies are described. The package includes an electrical die and an optical die coupled to and stacked with the electrical die. The electrical die includes circuitry to process and communicate electrical signals, and the optical die includes structures to transport optical signals. The electrical die has a smaller area than the optical die so that the optical die includes an exposed mezzanine which is configured with optical input/output ports. Additionally, the packaging can be configured to provide structural support against insertion forces for external optical connections.