Just want to correct this. If we are talking about types, we're pointing about DDR, DDR2, DDR3, SDRAM and so on. Mixing two different types of RAM is impossible. If your motherboard supports two memory types of RAM then you can use only one type of RAM. You can't install two types of RAM simultaneously because it will create a error or worst burn.I know you can mix diffrent types of ram ram but is it recomended?