Explain how virtual address is converted into physical address?

Answer 1

A Microprocessor provides a memory address (within the address space of that micro, which is related to the number of address pins of the micro. For instance 32 pins can generate 4GB of addresses). In a system with DRAM modules, each DRAm chip contributes with only one bit to compose the word. Each bit has its own address, each DRAM chip has its own address within a module and each module has its own address within the memory system. A DRAM chip is composed by N matrices, so there are "matrix address", line address and column address. There are so many addresses and control signals, and the microprocessor knows nothing about them. Thus, the system must contain a memory controller which translates the address provided by the processor (some times called virtual) into fisical memory address. These translations are made by the hardware (only).

Another history is the virtual memory, where there is a mapping between the address provided by the processor and the address where the data is stored (part in ram and part on disk). The address space is broken in pages, and a mapping unit (which can use a cache like memory - TLB) mantain information about which page is on the disk and witch is on the RAM. This system is a combination of hardware and operating system. The precise explanation can be found in any operating system book.

Sorry by the English.