Abbreviated frequently as a4x.
Boot firmware for the XR/station platform, written in xr17032 assembly and Jackal.
Place the new SDK at ../newsdk relative to this repository and build it. Then the following command, run from within this repository, should produce an a4x ROM at ./build/fre/a4x.rom:
../newsdk/bin/xrbt.exe build.xrbt a4x
The ability to hot-switch to the legacy a3x firmware can be added to an a4x ROM. The process for this is to build the old firmware, and look for a file called firmware.bin within its ./src/ subdirectory. Directly concatenate this file to the end of an a4x ROM to create a new ROM that can boot legacy operating systems.