Question about reading and writing data with sd card

[kof888]

Thanks for the quick response.
I also prefer sd card over tf card.
Because I have tested using the spi mode of the SD card to run commercial games on Saturn, for some games that do not require high reading speed, the result is still ok

So I want to try to modify and optimize the assembly instructions to read how fast it can be read on DC's commercial games (most of the functions have been slightly modified)

I would like to ask, for the iso loader using sd card, which system functions are replaced by the iso loader? Can you briefly write the process of the iso loader?
I want to test the reading speed of a certain dc commercial game, do you know of a more suitable game? (It is very intuitive to see whether it is stuck in the game, not CG)
I remember watching the speed comparison video of using sd card hdd and gdrom to read the game doa2, but I can’t seem to find it.