you only need one "boot.dol" file, and put it in SD:/apps/usbloader_gx/boot.dol
There are three different versions, but you will need only the boot.dol located in the IOS249 folder.
If you followed a softmod guide, you should have the correct cIOS installed in slot 249, so you need the "249" version.
The boot.elf is not needed at all, it's in the package for debugging purpose. only copy boot.dol on your SD or USB.
The other versions are there for users who don't have IOS249 or want to use a different IOS slot for launching the loader to speed up the loader's launch process (detecting drives, loading config file, unmount drive, reloading to a different user's IOS, remount drives). These 3 versions shouldn't be needed anymore, since r1218 it's using AHB access to read config file to speed launch.
For users who want to understand the differences, here is how the launching process worked/is working now:
Before r1218:
- using loader version 249, but using slot 250 in loader Settings (different IOS than loader's version):
reload from IOS58 to IOS249, detecting drives, loading config file, unmount drive, reloading to IOS250, remount drives
(6 processes)
- using loader version 250, matching the setting "slot 250" in loader's settings (same IOS than loader's version):
reload from IOS58 to IOS250, detecting drives, loading config file, no need to unmount/remount as it's already using correct IOS.
(3 processes)
Since 1218, if using AHB access:
- using any version, setting slot249 in loader's IOS and game's IOS:
detecting drives, loading config file, unmount drives, reload to IOS249, remount drives
(5 processes)
- using any version, setting slot58 in loader's IOS, and 249 in game's IOS
detecting drives, loading config file.
(2 processes)
IOS reloading to 249 is done only when launching a game
You can bypass AHB access by setting a IOS argument in the meta.xml, and have the same launch speed than before 1218
- using any version, setting any slot in loader's IOS
reload to argument's IOS, mount drive, read config
(3 processes)