Mix and match RAM is a gamble. It is possible your PC won't boot. It may not recognize all the RAM. Since it looks like you are trying to mix 4GB and 8GB RAM, it is hard to predict how your specific motherboard will react.
Mix and match RAM is a gamble. It is possible your PC won't boot. It may not recognize all the RAM. Since it looks like you are trying to mix 4GB and 8GB RAM, it is hard to predict how your specific motherboard will react.