It's interesting that they have a Raspberry Pi GPU backend, but neither an ARM backend nor any modern ISA. (such as x86-64, Aarch64, etc.) Is there any example program that actually runs on the rpi gpu? I skimped the website, but it is only mentioned in the release notes.

> Is there any example program that actually runs on the rpi gpu?

ThreadX.

https://en.wikipedia.org/wiki/ThreadX#Products_using_ThreadX

This RTOS, later rebranded Microsoft Azure RTOS, later still made FOSS:

https://www.theregister.com/2023/11/28/microsoft_opens_sourc...

ThreadX is the RasPi firmware. The GPU is the primary processor of the Pi: the ARM cores are essentially just co-processors.

Presumably someone wanted to write an RPi bootloader, which run on the GPU. Several universities have OS programming courses that use old 32-bit RPis. Not sure if anything was actually written though.

> Not sure if anything was actually written though.

The librerpi project

« librerpi is a FOSS boot firmware based on littlekernel for Raspberry Pi boards, it replaces the proprietary boot firmware normally used to boot. »

https://librerpi.github.io/

looks like they never went 64 bit