Test Drive Unlimited

[LunaMoo]

From the emulation point of view everything works correctly here. The problem is that the game game is using an effect that captures finished render and draws it again on top of itself which causes a loss of render res and also happen to be very demanding to emulate. The cheat just disables that effect completely at boot time and as far as I could tell nothing goes missing.

To extend on such effects, they are sometimes used in games ported to PSP from other platforms to simply stretch the render to match PSP screen, for example used in this japanese game which is a cheap PS1 port and renders everything in small 4:3 window which then get's resized and centered on the screen with some extra filtering. It's mostly 2D game so it's not as painful there, but does cause a loss of render resolution in character models.
In case of TDU however the render was already made at psp resolution and centered, so the effect potentially wasn't doing anything at all(other than disabling render resolution and requiring more powerful hardware to run it).