Steam Machine OCuLink eGPU Dock (M.2 → OCuLink) — Documentation Pack

This repository is a build + design documentation pack for a clean external eGPU solution for a Steam Machine that does not expose a native OCuLink port or USB4/Thunderbolt eGPU port on the rear I/O.

Core idea

• Use the Steam Machine’s internal M.2 Key‑M NVMe slot as the PCIe “exit” via an M.2 → OCuLink adapter
• Put the desktop GPU + PSU in an external dock enclosure
• Run SteamOS + games from an external USB‑C (10Gbps) NVMe SSD, optionally mounted inside the dock for a clean look

Steam Machine (internal M.2 used for OCuLink)      External Dock (GPU + PSU + SSD)
┌──────────────────────────────────────────┐      ┌───────────────────────────────────┐
│  M.2 Key‑M → OCuLink → rear panel port   │=====>│  OCuLink → PCIe x16 slot → GPU     │
│                                          │      │  PSU powers GPU + dock board      │
│  USB‑C (10Gbps) → external NVMe SSD      │----->│  (optional) USB‑C NVMe inside     │
└──────────────────────────────────────────┘      └───────────────────────────────────┘
                         HDMI/DP from GPU to display

Important warnings (read first)

• This is an invasive hardware mod (opening the Steam Machine, routing a PCIe cable, adding a panel port). You can void warranty and permanently damage hardware if done incorrectly.
• Treat the eGPU as semi‑permanent. Avoid “hot unplug”. Power down before disconnecting the OCuLink cable.
• Plan for cooling. A clean dock must still have a controlled intake/exhaust airflow path and dust filters.

(These warnings match the intent of the original concept guides this repo is based on.)

What’s inside this repo

• A complete set of Markdown docs you can copy into a GitHub repo.
• “Spec checklists” for Steam Machine requirements (what must be true for the mod to work).
• Dock enclosure design targets (GPU size classes, airflow layouts, rear port layout).
• Risk + thermal guidance + troubleshooting + validation steps.

Suggested repo structure

.
├─ README.md
├─ docs/
│  ├─ 00-Quickstart.md
│  ├─ 01-SteamMachine-Requirements.md
│  ├─ 02-BOM.md
│  ├─ 03-Internal-Mod.md
│  ├─ 04-Dock-Enclosure-Design.md
│  ├─ 05-Thermals.md
│  ├─ 06-Operations.md
│  ├─ 07-Troubleshooting.md
│  ├─ 08-Validation.md
│  ├─ 09-Legal-Safety.md
│  └─ 10-FAQ.md
└─ templates/
   ├─ Build-Checklist.md
   └─ GPU-Fit-Worksheet.md

Start here

Go to docs/00-Quickstart.md.

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Credits / source notes

This documentation pack is derived from two concept PDFs prepared for Marcelo Collado (Dec 16, 2025):

• SteamOS eGPU Clean Dock Build (M.2 → OCuLink concept)
• Steam Machine + OCuLink eGPU: Step‑by‑Step Visual Guide

It is not an official Valve document.