https://hungwenlin.com/blog/2009/%e5%b0%8d%e6%8a%97%e4%b8%89%e6%98%9f-%e5%8f%b0%e7%81%a3-dram-%e7%94%a2%e6%a5%ad%e8%a9%b2%e5%a6%82%e4%bd%95%e6%95%b4%e5%90%88%ef%bc%9f/