bandwidth for Cyclone IV(-8 grade) and 32-bit DDR2 SDRAM

anakha, thanks a lot for your comment!

You give me many good hints: IO voltage, pin assignment, ...

I would like to use parallel interface for ADC, but now it seems better to use LVDS to save pins.

besides -8 grade may be slow, I need to consider -6 grade for Cyclone IV.

I check and find Cyclone IV can only support up to 200MHz DDR2 clock, so perhaps I need Cyclone V which supports up to 400MHz DDR2 clock [@ Altera's External Memory Interface Solutions Center].