Mixing and matching RAM

[Anir]

Currently I have single stick 8 gigs DDR3 hyper x fury 1800 mhz in my PC installed, I have a another 4gb stick from an unknown vendor 1600 mhz stick that I got from my old home pc . Can I install the 4gb stick with 8gb stick, if yes, then in which slot should I install it, in dual channeled slot or independent slot ?

[Mira Yurizaki]

You can stick the 4GB stick in your PC. Your system though will run at DDR3-1600 at best, or DDR3-1333 at worst (DDR3-1333 is the "default" speed). If you don't have another pair for the 4GB, you'll run all sticks at single channel.

[ARikozuM]

25 minutes ago, M.Yurizaki said:

You can stick the 4GB stick in your PC. Your system though will run at DDR3-1600 at best, or DDR3-1333 at worst (DDR3-1333 is the "default" speed). If you don't have another pair for the 4GB, you'll run all sticks at single channel.

Unless you mentioned it, you can't run two densities in dual-channel.