atapi5 协议，是对硬盘/光盘进行编程的规范性文档。目前很多硬盘加密的程序都是基于该文档协议进行实现的。

PIO 0-5, MWDMA 0-2 and UDMA 0-6 timings (in nanoseconds). These were taken from ATA ATAPI-6 standard, rev 0a, except for PIO 5, which is a nonstandard extension and UDMA6, which is currently supported only by Maxtor drives.