I have built a game in Unity that uses OpenGL ES 1.1 for IOS. I have a nice constant frame rate of 30 until i place a semi transparent texture over the top on my entire scene. I expect the drop in frames is due to the blending overhead with sorting the frame buffer. On 4s and 3gs the frames stay at 30 but on the iPhone 4 the frame rate drops to 15-20. Probably due to the extra pixels in the retina compared to the 3gs and smaller cpu/gpu compared to the 4s.

I would like to know if there is anything i can do to try and increase the frame rate when a transparent texture is rendered on top of the entire scene.

Please not the the transparent texture overlay is a core part of the game and i can't disable anything else in the scene to speed things up. If its guaranteed to make a difference I guess I can switch to OpenGl ES 2.0 and write the shaders but i would prefer not to as i need to target older devices. I should add that the depth buffer is disabled and I'm blending using SrcAlpha One.

Any advice would be highly appreciated.

Cheers