How to connect two ddrs in a cyclone iii?

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Hi,

I plan to use two absolute ddrs in my system.

And I want to connect them in column banks and row banks,is it viable?

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If your ddrs have the same size you can double your column banks (for example). The highest bit you can use as an enable signal. If it is set you can enable ddr1. Otherwise you enable ddr2. Don´t forget to multiplex the output data.