Learning PSP assembly

[LunaMoo]

1. L0 = short from level 0, when there's more than one "Level-" and "Level+" buttons will activate so you can switch between them.
2. No, it's not an UMD address, it's an address in PSP RAM, textures are generally stored in VRAM for speed, but they can also be stored in RAM - which in normal commercial games will be 24 mb starting from 0x08800000, HD remasters, prototypes and some homebrew would get 56mb(those weird values comes from first 8 mb being reserved for kernel).
3. If I understand correctly that's just an offset to current framebuffer base. So somewhere before there was an instruction saying "Base: 090000" which would be shifted into 0x09000000 and then the offset for texture address which get's added to base to get the address.
4. You would have to use Disassembly(not GEDebugger) set a write breakpoint and check what code writes the texture there starting before the texture get's moved there, then trace back step by step what the game does moving it in memory, extracting and whatever else it could be doing. That might be bothersome and very time consuming since textures does not have to resemble images they are built from, there's lots of weird things psp games can do and there might be many steps to go back from a texture to an image file.
5. Yeah, check bat files which ppsspp is released with. You can log breakpoints as well ~ including values of registers, when setting or editing execute breakpoint, just type into log fmt some description and registers between {}, for example: label1 {a1}, label2 {t2}, note that verbose log can be pretty heavy and in some games breakpoints might cause instability, so stuff might ocassionally crash;p.


When wanting to mess with games textures if you wouldn't care about real hardware, you could also consider just using texture replacement ~ under tools->dev tools there are some options for it, also this thread has lots of info about it. Might be troublesome to use in some games that modify textures or store random and changing data over some unused parts of textures, but in general it's pretty nice feature that avoids all the trouble of messing with game files also allowing custom HD textures.