both will work, the ddr3 just has faster memory on it, which the GPU supports, the motherboard doesn't come into the equation, though your motherboard might not take full advantage of the ddr3, but it would work just fine.
both will work, the ddr3 just has faster memory on it, which the GPU supports, the motherboard doesn't come into the equation, though your motherboard might not take full advantage of the ddr3, but it would work just fine.