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I know this is not the answer that you want, but It may or may not work fine. Ideally you should upgrade in matched pairs; with different sizes and (potentially) manufacturers, there is a chance it could cause stability issues. Common things I’ve seen happen are just getting stuck on a boot screen or BSOD. On the other hand, I’ve also seen it work fine. I think there are just too many variable to give a definitive answer. If it was me, since you already have them laying around, I would just give it a try, you probably aren’t going to hurt anything.