How does Dolphin increase internal resolution?

[MarkH123456]

How does Dolphin increase internal resolution and use custom textures when the Gamecube only has 24mb of memory and custom textures can be several gigabytes in size?

[JosJuice]

The increased resolution frame buffers and the custom textures are stored in additional memory which doesn't exist on a real GameCube and which can't be directly accessed by the emulated software.