Can using 2 pairs of different speed of DDR3 ram (each in dual channel) cause any issues?

Question

I want to expand the memory on my computer, I've got a pair of 1600mhz 4 gig DDR3 ram running in dual channel currently, the motherboard can support speeds up to over 2000mhz (can't recall the exact upper end) and has 4 memory sockets, can I safely upgrade with a pair of another 4 gig DDR3 but with higher speeds? would I lose the speed benefit due to having the slower pair? (aiming to go with same brand, almost identical pair, just higher speed).

Answer 1

The new RAM sticks will run at the slowest frequency, so 1600Mhz. You could overclock the old ones to match the frequency of the new ones.

Answer 2

I'm pretty sure this is specifically why they specify what speeds of ram are supported. I don't see a reason why a slower ram card would slow down a faster neighbor. I can't say for sure if the board would prioritize the faster ram card but as long as you fall within supported limits of the board, you're gonna see a benefit.

On just about every laptop I've owned, they've come with two slots (2 GB) each and I normally only max out one of the two slots since 10-18 GB is plenty for me. That all being said, I've had no problems with this setup so far.

Mathematically speaking, there is benefit to having same sizes since you're not trying to manage a lot more memory on one slot while the neighboring slot (which is just as fast) only has to deal with a fraction of the ram usage.

All in all, unless you have a weird board that was designed oddly to sync the ram frequencies, there really shouldn't be a downfall to mixing two ram cards that work at different frequencies as long as that is technically the best that you personally are gonna provide the machine to work with.