how can i set breakpoint before the game loads any assets?

[grief3r]

im trying to figure out how different games unpack the data found under the usrdir directory , however setting a break point to the default load adress (08804000) and dumping the ram seems to indicate this data has already been unpacked

example. if i wanted to view the assembly code in mgspw right as the game reads the first byte from slot.dat under PSP_GAME\USRDIR how would i go about doing this?