#648 – The RP1 and beyond with the Raspberry Pi Hardware team
Oct 23, 2023
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James Adams and Liam Fraser from the Raspberry Pi Hardware team discuss the RP1 chip, RP2040 updates, sourcing chips, IP block updates, prototyping on FPGAs, openness in Raspberry Pi's hardware, and hidden signatures on the Raspberry Pi board.
RP-1 serves as a Southbridge or IO hub, complementing the Broadcom processor on Raspberry Pi devices, improving chip design efficiency and cost-effectiveness.
Raspberry Pi aims to maintain openness in its chip designs and software, while facing restrictions due to IP agreements, and plans for future chip generations.
The chip industry is dealing with a severe silicon shortage, emphasizing the importance of integrating IP blocks like USB and Ethernet controllers into chip designs.
Deep dives
The Genesis of RP-1 and the Chip Design Team
The podcast episode delves into the origins of RP-1, the first Raspberry Pi silicon, and the process of building a chip design team from scratch. The team initially consisted of three contractors who were brought in to explore the possibilities of repurposing spare MIPI channels for data transfer. As the project progressed, more detailed specifications were developed, and the team grew in size. The episode highlights the challenges faced during the creation of RP-1 and emphasizes the importance of leveraging expertise and finding innovative ways to optimize chip design.
The Role of RP-1 as a Southbridge or IO Hub
RP-1 serves as a Southbridge or IO hub, complementing the Broadcom processor on Raspberry Pi devices. It takes on the role of managing input and output operations, including USB, PCI Express, and other peripheral functionalities. The episode explains that RP-1 is designed to offload the IO-related tasks from the main processor, allowing for more efficient and cost-effective chip design. By separating the IO functionalities into a dedicated chip, Raspberry Pi can focus on refining and improving the main processor and other custom features.
Openness and Future Prospects
The podcast explores Raspberry Pi's commitment to openness in its chip designs and software. While some aspects of the chip are restricted due to IP agreements, Raspberry Pi aims to make its platform as open as possible. The episode discusses the potential for future chip designs and mentions the likelihood of new generations of microcontrollers. It also highlights the growing interest in Raspberry Pi's PIO (Programmable PIO) feature and showcases some innovative applications like Ethernet over fiber and logic analyzers that have been developed using RP2040's PIO capabilities.
The Challenges of Silicon Shortage and the Importance of IP Integration
The podcast episode discusses the challenges faced by chip manufacturers due to the silicon shortage and highlights the importance of integrating IP (intellectual property) into chip designs. The speaker mentions that the industry is experiencing a severe silicon shortage, which has led to difficulties in sourcing chips. They emphasize the importance of integrating IP blocks, such as USB and Ethernet controllers, into chip designs. The use of IP from companies like Synopsys is mentioned as a common practice. The speaker also explains that the chip design process involves selecting the latest version of an IP, freezing the design before manufacturing, and considering bug fixes and version changes when using IP. The speaker mentions the benefits of using FPGA prototypes for software testing and highlights the complexity of designing chips that involve both digital and analog components.
The Raspberry Pi Design Process and Hardware Development
The podcast episode provides insights into the design process and hardware development of Raspberry Pi boards. The speakers discuss the considerations involved in choosing the components for the Raspberry Pi 5, highlighting the importance of optimizing the layout to ensure signal integrity and avoid design issues. They explain how Raspberry Pi boards make use of proven IP, including ARM cores and various controllers. The discussion also touches on the maturity and prevalence of ARM-based solutions compared to RISC-V. The speakers express interest in RISC-V technology but acknowledge the current advantages of ARM, including mature software tools and a well-established ecosystem. The episode concludes with the mention of a hidden signature on Raspberry Pi boards as a personalized touch added by one of the designers.
