https://web.archive.org/web/20120704194440/http://www.r4sdhc.com/index.asp

cheats (original):

_system_/usrcheat.dat
_system_/cheat.dat

original R4SDHC should use R4SDHC YSMenu

cheats:
R4iMenu/usrcheat.dat

YSMenu (V2.10T and V2.20T UNTESTED! please open issue if not working):
replace all files with R4i-SDHC YSMenu