It's not that your 3.6/3.8 isn't enough, it's that your AMD Bulldozer based CPU needs something close to 5ghz for true full-speed PS2 emulation, whereas Intel Core i5 2500k is more than capable of it at stock settings.
Basically, Bulldozer is ****. Sorry for your loss. That's not an AMD vs Intel thing, it's just the truth.
The following AMD configurations have, under some circumstances, managed full speed PS2 emulation:
AMD Phenom II X4 955 BE @ 4.3 / 4.2 GHz OC 63.24 FPS / 61.30 FPS
AMD FX-8120 @ 4.7 / 4.6 GHz OC (2 Modules) 62.02 FPS / 60.72 FPS
AMD Phenom II X6 1090T @ 4.2 GHz OC 60.84 FPS
AMD Phenom II X2 555 Black Edition @ 4.3 GHz OC 60.04 FPS
With 60fps being "full speed".
