I wish kentoot could confirm there is a "per game" speed setting. Otherwise correcting just save sizes would only partially fix the problem. According to a sarah99 recent post, it seems "fastest is not always the best". It makes sense, as this could be causing unstability and being the reason of white screens in Mario Kart for those getting them.
Well, I did try highlighting different games and then changing the SD speed setting & saving the option menu, but I think there's no change to the ndsinfo.dat file. For now I have to conclude that the SD speed setting is not game related, but pretty much a global thing, just as Sarah99 pointed out.
The SD speed setting, just like the other menu items (ICO Modality, File Sort, Language etc.), is being saved into a different file, menusave.sav.
For example, inside the menusave.sav file :
ICO Modality (address : 08 hex)
data at address 08 hex :
- No ICO : 00 hex
- Small ICO : 01 hex
- Big ICO : 02 hex
File Sort (address : 0C hex)
data at address 0C hex :
- File Name : 00 hex
- Time : 01 hex
SD Speed (address : 14 hex)
data at address 14 hex :
- 1X ~ 5X : 00 ~ 04 hex
I guess the SD speed setting can be game specific, it doesn't have to be a global thingy. But for now it's global.