Load64 is a sorry excuse for a second stage bootloader. It has no configuration, no filesystem support. It can load its kernels only from the volume header.
However it is simple, it is very fast, and requires no porting to use it on a new 64-bit ARCS platform. It used to be the only bootloader that can load Linux kernels on Octane machines. It is also a convenient starting point for more advanced excursions into the land of bootloading.
You don't want to use it anymore. It has been superseded by ARCLoad.