Chestnut – An eGPU Dock with Open-Source Firmware

George Hotz's comma.ai has released Chestnut, an eGPU dock that allows users to directly read and control the firmware of USB4 bridge chips. Beyond being a simple graphics card enclosure, the product is designed to give developers access to the hardware control plane.

Key Features and Purpose

• Model Performance Scaling: Aims to raise the existing power limit of around 10W to approximately 100W to run large driving models with 1B parameters included in openpilot 0.11.2. This model has 30 times more parameters and 100 times more FLOPs than existing on-device models.
• Open-Source Firmware: C-based firmware for ASMedia's ASM2464PD bridge controller has been published on GitHub (tinygrad organization). This allows users to access PCIe BARs or perform debugging and control.
• Product Configurations
  • Tiny chestnut ($249): Dock-only product.
  • Chestnut “ready to drive” ($799): Includes AMD Radeon RX 9060 8GB and cabling/mounting hardware.

Technical Significance While existing eGPU enclosures had closed firmware, Chestnut enables hardware-level debugging and control by making the firmware public. Although gaming performance may be limited due to USB4 bandwidth constraints, it holds significant value as infrastructure for running large AI models in edge environments (such as vehicles).