Full Amount of RAM Not Detected

If I use both ram in both slots, the computer recognizes it as 16gb but after restarting, it reverts back to 8gb even though they're in dual

dosto is video mein main aapko Apne computer mein do Ram ek sath Kaise chalana hai

ramses slot I hear about this frequently The computer did not have RAM in the slot from the factory, and

rama slot If I use both ram in both slots, the computer recognizes it as 16gb but after restarting, it reverts back to 8gb even though they're in dual