The Xtreme is always on, so as long as the battery does not die, the contents of the filesystem (which uses 1/4th of RAM) is preserved. The only way to get new apps on an emulated Xtreme is to "edit" the ramdisk image using imgtool.

All I am doing is

Code
void *ptr = ram_get_ptr(machine.device(RAM_TAG));
file->read( ptr, 512 * 1024);
FYI. When doing "load ramdisk.bin,400000,80000" in the debugger window, the ramdisk contents in RAM does not get byteswapped.