https://blog.wongcw.com/2019/06/12/%e5%90%88%e8%82%a5%e9%95%b7%e9%91%ab%e5%9c%8b%e7%94%a28gb-ddr4%e5%85%a7%e5%ad%98%e5%b9%b4%e5%ba%95%e9%87%8f%e7%94%a2/