BF609+ov5640 Frame Rate adjust


I am using BF609 as image processor with camera (ov5640 by DVP port). Until now, I have basically implemented ov5640 driver in BF609 and can display image with 640x480 in 25fps. However, if I want to increase frame rate to 60fps or even 30fps, it can not display anything. I only adjust system clock part. I used ov9650 before, and it could display image with 640x480 in 30fps. I searched this problem online, it might be the SRAM problem, but I am not sure. I am thinking if I can use 640x480 image in 30fps from ov9650, why not the same frame rate of ov5640? My goal is to increase frame rate from 25fps to 60fps in ov5640, and need to reach first step that is 30fps with 640x480 pixels.