Performance issue on ZenFone 2

[Livy.]

I've bought an Asus ZenFone 2 ZE551ML (highest model). The specs are good:

• Intel Atom Z3580 (4 cores, 500 - 2333 Mhz)
• PowerVR Rogue G6430 (457 - ??? Mhz)
• 4 GiB LPDDR3 SDRAM (does not matter)
• 1920x1080 display @ 60 Hz (does not matter)
  

I have no serious plan of playing PSP games until I get a gamepad. However it does not hurt trying things out. I have performance issue in all games. In God of War games, the framerate ranges from 15 to 20/60 FPS (native res). And in lightweight games such as The 3rd Birthday, the framerate drops below full speed when internal resolution is set to above 2x.

This phone is probably more powerful than my current 5 year old laptop (Phenom 2 X4 @ 2.0 Ghz, AMD Radeon HD 4570M). I've played all these games on my laptop without any major problem. GoW games did slow down a bit due to my crappy GPU, but it is still playable. The 3rd Birthday ran at full speed at 3x internal res.

I even tried to reset PPSSPP settings to default (1x internal res, 2x display res). The phone battery mode is set to High Performance, still to no avail. What should be the cause of the problem?

Edit: PPSSPP version is 1.0.1, downloaded from Android Market. And I did not do smart things like turning JIT off, setting the resolution to 3840x2160 or something similar.