Raspberry Pi Unveils First RISC-V Multicore Chip

Raspberry Pi has made significant advancements in chip development by introducing a quad-core microcontroller featuring two ARM Cortex-M33 cores and two in-house RISC-V cores. The newly launched $5 Raspberry Pi Pico 2 board is powered by the RISC-V RP2350 microcontroller and is set to be followed by a wireless version known as the Pico 2 W, which will incorporate a modem from Infineon Technologies.

The RP2350 microcontroller boasts several enhancements over its predecessor, the RP2040, which was released over three years ago. The RP2350 is twice the die size, operates at a higher core clock speed of 150MHz, offers double the memory with 520KB of SRAM in ten banks, and introduces new security features. Despite the increased die size of 5.3mm2 compared to the RP2040's 2mm2, the entry-level RP2350A variant will only cost ten cents more, priced at $0.80 in 3,400-unit reels or $1.10 for single-unit quantities.

In addition to the ARM Cortex-M33 cores, the RP2350 integrates two RISC-V cores that can be dynamically allocated during boot time. The boot ROM is designed to automatically detect the architecture for a second-stage binary, facilitating a seamless transition into the appropriate mode.

The Hazard3 cores, developed by Luke Wren, a Principal Engineer in the Raspberry Pi chip team, are a standout feature of the RP2350. Utilizing the RISC-V open instruction set architecture (ISA), the Hazard3 cores are optimized for performance and code density, implementing the RV32I instruction set along with various standard extensions. This enables software developers to explore the RISC-V architecture in a stable and well-supported environment, potentially paving the way for broader adoption of the Hazard3 core in other devices.

The security architecture of the RP2350 is centered around Arm TrustZone for Cortex-M, offering features such as signed boot support, on-chip antifuse one-time-programmable (OTP) memory, SHA-256 acceleration, and a hardware true random number generator (TRNG). Additionally, the chip incorporates an on-chip switch-mode power supply and a low-quiescent-current low drop-out (LDO) regulator developed in collaboration with Dolphin Design in France.