The term "ISO" refers to a disc image file—a digital clone of the original UMD (Universal Media Disc). Why do players seek out the Asphalt 6 ISO today?
When searching for "PSP ISO downloads," you will encounter many websites hosting ROMs. It is important to be cautious:
While the iOS version used touch tilt controls (often frustrating), the PSP version was universally praised for its physical controls. Using the analog stick for steering and the face buttons for nitro/drift provided a precision that touchscreens couldn't match.
Furthermore, the PSP version supported Ad Hoc multiplayer for up to 6 players. Before online play was standardized, sitting in a schoolyard with four friends racing on local Wi-Fi was the definition of gaming bliss.

