u/Kitchen-Currency-796

I have a pc running i7 4600U with 12GB DDR3L RAM, it had 8GB RAM single channel then I added another RAM 4GB for a total of 12GB. This pc is supposed to run at 1600MHz but through an app it says the ram runs at 800MHz. I heard running at dual memory it speed performance but the freq dropped to 800 how can i run them both at 1600MHz