Perfect Dark runs at 60fps, GoldenEye runs at 3-4fps

This is in PJ64 1.7.0.49 beta by the way. Is there any specific setting that needs to be set differently for these two games, like a graphics plugin option? I can't understand why PD runs fine and GE is unplayable when they use similar engines. I think the only setting I changed for PD was the Direct3D Clear Mode to fix the sky but this setting doesn't help with GE speed. Changing the resolution from 1920x1080 to 320x240 makes NO difference whatsoever - still says 3.00 VI/s. PJ64 is using 100% of a single CPU core whilst this is happening btw and it runs fine in the intro and menus - it's just when I load a level that it starts to massively slow down.

PC specs: i7 920 @ 4GHz, 6GB RAM, Windows 7 x64.

Thanks for any ideas.