Accessing hard disk

Question

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。

Answer 1

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.

There are various addressing schemes for Hard-disks as well, such as LBA, CHS etc, which themselves run into limitations from time to time.

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

Read this and this .