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Paging Examples

Paging Examples. Assume a page size of 1K and a 15-bit logical address space. How many pages are in the system?. Paging Examples. Assume a page size of 1K and a 15-bit logical address space. How many pages are in the system?

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Paging Examples

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  1. Paging Examples Assume a page size of 1K and a 15-bit logical address space. How many pages are in the system?

  2. Paging Examples Assume a page size of 1K and a 15-bit logical address space. How many pages are in the system? How many bits are required to address each byte within a 1024-byte page?

  3. Paging Examples Assume a page size of 1K and a 15-bit logical address space. How many pages are in the system? How many bits are required to address each byte within a 1024-byte page? 10 (2^10 = 1024). This leaves 5 bits for page number. So, How many pages are in the system?

  4. Paging Examples Assume a page size of 1K and a 15-bit logical address space. How many pages are in the system? How many bits are required to address each byte within a 1024-byte page? 10 (2^10 = 1024). This leaves 5 bits for page number. So, How many pages are in the system? 32 (2^5 = 32)

  5. Now consider a 15-bit address space with 8 logical pages. How large are the pages?

  6. Assuming a 15-bit address space with 8 logical pages. How large are the pages? • Answer: 2^12 = 4K. It takes 3 bits to reference 8 logical pages (2^3 = 8). This leaves 12 bits for the page size and thus pages are 2^12.

  7. Consider logical address 2049 and the following page table for some process P0. Assume a 15-bit address space with a page size of 1K. What is the physical address to which logical address 2049 will be mapped? 8 0 3

  8. Consider logical address 2049 and the following page table for some process P0. Assume a 15-bit address space with a page size of 1K. What is the physical address to which logical address 2049 will be mapped? Logical Pages Step 1. Convert logical address to binary: Logical address: 000100000000001 0 1 2 3 4 8 0 3

  9. 8 0 3 Logical Pages Step2. Determine the logical page number: Since there are 5-bits allocated to the logical page, the address is broken up as follows: 00010 0000000001 Logical page number offset within page 0 1 2 3 4

  10. 8 0 3 00010 00011 Step 3. Use logical page number as an index into the page table to get physical page number. Logical Address: 00010 0000000001

  11. 8 0 3 00010 000110000000001 Step 4. Concatenate offset with physical page frame number Logical Address 000100000000001

  12. 8 P0.1 0 3 0 1 2 3 4 0 1024 2048 3072 P0.2 4096 000110000000001 = 3073

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