RISC OS Pi is the latest version of the RISC OS designed for Raspberry Pi. RISC OS Pi brings an alternative desktop environment and a stack of heavily functional applications for the Pi board. If creating a boot image is too much work, you can get a specially prepared SD card preloaded with the RISC OS.
The USP of this platform is that it’s light and super responsive. It also offers a minimized version called RISC OS Pico that’s just 3.5 MB in size (for ZIP file) and is targeted for Pi hackers and modders. RISC OS Pi requires a SD card of minimum 2 GB to run on Raspberry Pi.