David Slik's Asynchronous Array of Raspberry Pi Picos, AARPP, Is a Tile-Based RP2040 Supercomputer

With 32 Arm Cortex-M0+ cores per tile, the AARPP design could power the world's first super-microcontroller using 1980s supercomputing tech.

Engineer David Slik is working on a microcontroller board with a difference, connecting a grid of RP2040 microcontrollers to create the "Asynchronous Array of Raspberry Pi Picos," or AARPP.

Released late last month, the RP2040 is the first microcontroller and first in-house silicon to be launched by Raspberry Pi — an organization better known for single-board computers. While the launch focused primarily on the Raspberry Pi Pico development board and embeddable module, the RP2040 itself is also to be made available to purchase as a bare chip — something companies from Adafruit to SparkFun have already confirmed they are planning to exploit with a range of in-house RP2040-powered board designs.

Slik's AARPP, though, is unique: It hosts not just one RP2040 chip, but an array of 16 arranged in a 4x4 grid for a total of 32 Arm Cortex-M0+ cores per tile. "Exactly what you need for low-cost data flow/distributed/SIMD [Single Instruction Multiple Data]/Transputer-emulation needs," Slik explains.

The design, as Slik intimates, mimics that of the Inmos Transputer family, launched in the 1980s and designed for highly-parallel computing: A Transputer motherboard would hold an array comprised of multiple CPUs, all communicating with each other and operating in parallel. The same core concept underpins modern GPUs and more esoteric high-performance computing architectures like Tilera, now owned by Mellanox.

"[I] need to do another spin of the board design so that Pi 2040s in the first row can use SWD [Serial Wire Debug] to program/debug North and East Pi 2040s," Slik notes, "and Pi 2040s in every other row can use SWD to program/debug East Pi 2040s. From a software side, I'd use one core for routing/process management/debug/health monitoring/etc, and the second core for running user programs."

Slik has not yet released additional detail publicly, but can be followed on Twitter for more information.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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