Can I use 1333 MHz and 1600 MHz RAM together?

I currently have 2x1GG 1333MHz DDR3 strips. I plan to purchase a further 2x4GG 1600Mhz strips. Will I be able to use both sets of RAM in my PC together? Will they both be limited to 1333Mhz?

• Old RAM: Corsair cm3x1024-1333c9dhx
• New RAM: Corsair CMX8GX3M2A1600C9
• Motherboard: Asus p5k3 Deluxe

Solution 1:

Mixing RAM sticks of different timings may or may not work. Memory has a lot of other timings besides the MHz rating and if the memory controller cannot find a set of timings that both sets of modules supports then your computer may not boot or may act very weirdly.

Otherwise it may be that the different set work perfectly well together, in which case they will work at the highest speed supported by the slowest module. In your case this will be 1333.

So buying 1600 RAM that you intend to use with 1333 will be a waste of money unless the 1600 is actually cheaper, which wouldn't surprise me these days.

If you truly are going to get 2x4Gb strips, then you're not going to notice much difference between 8Gb and 10Gb. I'd just chuck the 2x1Gb and let the 4Gb sticks run at full speed.