Question

With a neat sketch explain how virtual to physical mapping is done using page tables for the following case

virtual memory - 16K, Page size - 2K, physical memory - 8K.
Points will be given on the following basis
1. neatly draw the virtual and physical address space
2. how bits are used in MMU (page numbers and offset)
3. Give an example using an instruction to transform a virtual address to a physical address (you can use MOV REG, x, where x can be any address say 8200).

Answer 1

To map virtual memory to physical memory, a page table is used. The virtual address space is divided into page numbers and offsets to identify the corresponding physical address. An example using a virtual address of 8200 demonstrates the conversion process.

Step-by-step explanation:

To map virtual memory to physical memory, a page table is used. In this case, the virtual memory is 16K and the page size is 2K. The physical memory is 8K.

1. Neatly draw the virtual and physical address space:

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• Virtual Address Space:
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• 0 - 16K
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• Physical Address Space:
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• 0 - 8K

2. How bits are used in MMU (page numbers and offset):

The virtual address is divided into a page number and an offset. The page number identifies the page in the page table, and the offset specifies the location within that page.

3. Give an example using an instruction to transform a virtual address to a physical address:

Let's assume the virtual address is 8200. To convert this to a physical address, we need to determine the page number and offset. Since the page size is 2K, the offset will be 200. The page number can be calculated by dividing the virtual address by the page size: 8200 / 2000 = 4. Therefore, the virtual address maps to page 4 in the page table. To find the corresponding physical address, we use the page table to look up the frame number for page 4. Let's assume the frame number is 2. The physical address is then calculated as: (frame number * page size) + offset = (2 * 2000) + 200 = 4400 + 200 = 4600.