Baochip-1x: What It Is, Why I'm Doing It Now and How It Came About
The Baochip-1x introduces a Memory Management Unit (MMU) to microcontrollers, challenging the long-standing industry norm of embedded systems lacking this crucial security feature. Leveraging the freedom of RISC-V, its creator "bunnie" details the pragmatic approach of embedding a partially open-source core onto another company's chip. This story resonates on HN for its blend of hardware design ingenuity, advocacy for open silicon, and a clever workaround to bring advanced capabilities to a broader developer community.
The Lowdown
The Baochip-1x is a new microcontroller project spearheaded by Andrew "bunnie" Huang, aiming to bring advanced software assurance capabilities to the embedded space by integrating a Memory Management Unit (MMU). This update provides the backstory and rationale behind the project, highlighting its unique technical features and the pragmatic engineering decisions that made it possible.
- The core differentiating feature of the Baochip-1x is its Memory Management Unit (MMU), which is rare in its performance and integration class of microcontrollers. An MMU enables secure, loadable applications by providing virtual memory spaces, a concept proven over decades in modern operating systems.
- Bunnie argues that while newer memory protection technologies exist, the MMU remains composable and essential for features like transparent address space relocation and swap memory, which are typically absent in small embedded systems.
- The historical absence of MMUs in embedded systems is traced back to ARM's strategy, where M-series cores were intentionally restricted from having an MMU to prevent competition with their higher-end A-series. Open architectures like RISC-V now allow designers to break from this convention.
- The chip's development utilized a "hitchhiking" strategy, where the Baochip-1x's RISC-V CPU and features were incorporated into the unused floorplan space of a larger 22nm chip designed by Crossbar, Inc., significantly reducing production costs.
- Baochip-1x champions a "partially open RTL" approach: all compute elements are open for inspection and simulation, while closed components like the AXI bus, USB PHY, and analog parts are considered "wires" that do not transform data. This is presented as a pragmatic step toward a fully open-source silicon future.
- The project plans to make thousands of production-qualified Baochip-1x chips available through a pre-order campaign, aiming to build a developer community around the hardware and support open-source operating systems like the Rust-based Xous OS.
The Baochip-1x represents a significant effort to democratize advanced hardware features and foster an open-source ecosystem in embedded systems, challenging proprietary norms through innovative design and manufacturing strategies.