存取硬盘 [英] Accessing hard disk
问题描述
CPU如何通过仅32位的寄存器和数据总线来解决数百GB硬盘上的远程存储器位置.
How does the CPU manage to address the distant memory locations on a several hundred giga bytes of hard disk with registers and data bus of 32 bits only.
推荐答案
RAM直接映射到处理器的地址/数据总线.硬盘不是.它们与磁盘控制器(IDE，SATA，SCSI等)接口.磁盘控制器将CPU与其一起工作的较小块中的数据复制到RAM中或从中复制数据.
RAM is directly mapped into the processor's address/data bus. Hard drives are not. They interface to a disk controller (IDE, SATA, SCSI, etc). The disk controller copies data to/from RAM in smaller blocks where the CPU works with it.
也有用于硬盘的各种寻址方案，例如LBA，CHS等，它们本身有时会遇到限制.
There are various addressing schemes for Hard-disks as well, such as LBA, CHS etc, which themselves run into limitations from time to time.
因此，处理器只需要访问高速缓存和RAM，因为HDD本身太慢了. 32位CPU一次只能访问4 GB的内存，这是这些系统上物理内存大小的限制. 因此，顺序是
Hence, the processor only needs to access the caches and RAM as the HDD itself is too slow for it. The 32 bit CPU can access just 4 GB of memory at a time, which is the limit on the size of physical memory on these systems. Hence, the sequence is
HDD-->RAM-->Caches-->Processor
