VIP FrameBuffer - How do you think it is accessing the SDRAM?

Is the 65 MHz you mentioned before taking into account the horizontal blanking? For example, if your pixel clock is 65 MHz, the average rate per line would be less if there is a horizontal blanking interval.

Also, have you tried to optimize the way pixels are packed into words by the frame buffer? For example, if you set the word size to 32 bit, you are wasting 25% of your bandwidth storing 24 bit pixels into 32 bit words. If you increased the word size to 128 bit, you could store 5 pixels in one word which would only waste 6.25%.

Even taking into account the above, you may still not have enough bandwidth. But I thought I would mention it just in case.

If you need to, reducing the bit depth may have less impact than you might think. 16 bit RGB tends to look noticeably bad depending on the image, but 16 bit 422 YCrCb looks fairly good.