problem with LCD Refreshing rate

Hello,

I recently designed a model in Quartus which connects to a color LCD device and shows what ever is on the SRAM.

I am using the NIOS processor to fill the RAM with the relevent Data (PICS,ANIMATIONS and so).

One problem is that the reading cycle time of a byte is 55nsec.

the LCD can work up to 33MHZ(840X480) so I'm not able to fully use the LCD's Resolution(I'm using 8 MHZ which is 480X272 Res).

another Problem is the Data size (24 bits - 8 red + 8 green + 8 blue).

I cant write 2 cycles on the sram for every Pixel because it doesent match the 8 MHZ timing.

so what i did is to normalize the data bits to 15 bits per each pixel (5r+5g+5b) and decrase the lcd's speed to 8 mhz

for every screen I want to load I need to fill up the ram with 480*272 Addreses(130.5Kbytes).

The problem is that the NIOS clk seem to be 50MHZ but the actual one is much slower,so it takes me about 2 secs to fill up the sram.

that gives me a slow refresh rate on the LCD.

are there any sugesstions to make the NIOS RUN faster?

Is my techniqe OK?

are there any other good methods to work with LCD so I would able to exploit the SPEED and pixel bits?

thanks for all the helpers,

Asaf