tBA maximum 50ms and tBD maximum 1s are mentioned already in the Boot topic. tBA means the time of Boot Answering to send back 5-bit boot acknowledge， tBD means the first prepare time needed for Boot Data out.
之前移动设备的存储方案都使用eMMC，采用并行架构，最高存储速度也不过400MB/s，继续发展的潜力有限。现在，全新的UFS存储技术带着全新设计的串行存储架构正式面世。硬盘之前使用的是并行传输的IDE接口，后来全部转为目前的串行SATA接口。
