PPSSPP won't work on HTC One M7

[Unknown1]

Hey all, I've read a lot of people have PPSSPP working on their HTC One's (M7), but when I play games on mine its very laggy, audio and video playback stops and starts so much that its not playable at all.

In case I've done something wrong here is what I've done:

Download PPSSPP, got the ISO's off my UMD's (Fifa 12 and Need For Speed Carbon) downloaded and ISO compressor which compresses files to CSO (which I've read PPSSPP plays), transferred games via USB to my phone.

PPSSPP works fine until the game is properly underway ie. Fia 12 menu (audio playback, speed, etc.) all works fine until the teams kick off. As soon as they do and the match is underway, its so slow and laggy its nowhere near playable.

Initial thought was maybe compressing to CSO is why it won't play properly?

Any help really appreciated