Using both 667 & 800 ddr2 ram on same motherboard??? - DDR2 - Memory

So you have two Corsair cm2x2048-6400c5, one Hynix PC2-6400U-666-12 and one Nanya PC2-6400U-666-13 and all are 800 MHZ. Why did you mention 667 MHz in the title? I don't understand the choice of Corsair cm2x2048-6400c5 with the other modules ...

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