• cdrom - All things CD-Rom related, such as the ISO9660 filesystem parser, the iso parsers, and other related things.
• core - The core of the emulator, such as the CPU, the memory, the BIOS, etc. Probably should be more split off.
• gpu - The GPU emulation.
• gui - All of the GUI code.
• lua - The Lua support library, with wrappers for non-emulation related things.
• main - The main entry point of the software, with the various wrappers for the different platforms.
• mips - The MIPS library code, such as OpenBIOS, psyqo, etc.
• spu - The SPU emulation.
• support - Various generic support libraries, such as intrusive lists, file classes, etc.
• supportpsx - Various support libraries, designed for the PSX, such as the MIPS assembler, etc.