Hello I want to upgrade my RAM from 1x8 to 2x8 and im curious if a can use different(?) RAM sticks. Both are from GoodRam but one is called GoodRam DDR4 8GB 2133 CL15 (GR2133D464L15/8G) and second one GoodRam DDR4 8GB 2133 CL15 (GR2133D464L15S/8G),the difference is ''S''... what does ''S'' mean?