Leapster Explorer: Emerald Boot
Emerald Boot is the name of the boot loader that comes installed on the Leapster Explorer. This is the software that takes care of getting the CPU up and running, and loads the kernel for execution.
LeapFrog have made no provisions to upgrade Emerald Boot on the Leapster Explorer. The only way to install a different version, is to flash it to the NOR storage yourself. The Emerald Boot source code is included in the LeapFrog releases. To get the source, download the LF-Linux-* archive of the release you desire to use.
While strictly speaking UART booting of Emerald Boot is not possible on the Pollux because of the file size, and hardware restrictions. But if you are handy with a soldering iron, the hardware restrictions can be dealt with, and through the use of a helper program, the boot loader can be uploaded and ran, in a very similar fashion as UART booting. Making testing non-destructive and a lot easier.