Short Note on Translation Lookaside Buffer.
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  • Operating system divides each incoming programs into pages of equal size. the sections of the disks are called as blocks or sector.

  • The section of main memory are called as page frame, one sector will hold one page of job instruction and fit into one page of memory.

  • Fixed size blocks in main memory are called page frame and breaking of logical memory into blocks of same size are called pages.

  • CPU generates, logical address containing page number and an effect. the page number is used to retrieve the frame number from a page table which gives the page addr so that physical address is calculated as base + offset.

  • To implement the page table in memory set of register are used of page table size increases their register are not suitable, then special purpose hardware cache is used for page table called as translation look aside buffer (TLB)

  • TLB is very effective in improving the performance of the page frame access. the cache badtn is implemented in a technology which is faster then the primary memory technology.

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Paging with TLB

  • The TLB contents may be controlled by the OS, or by H/W, depending on the architecture of the system.

  • When a page is first translated into page frame, the map is read from primary memory into TLB.

  • The TLB contains the page number, page frame physical address etc.

  • The page mapping mechanism first tries to find page number, then it is called page.

  • If the TLB does not contain an entry for page P, then it is called as page miss or TLB miss.

  • In case of TLB mis, the OS locates the page table entry in the primary memory, which increases execution time.

  • The TLB is associative high opad memory and it is used to store a few of the translation table entries. it is vert fast, but very few entries on each memory reference.

  • First ask TLB if is knows about the page and process.

  • If TLB has no information for page, must go through page and segment table to get information.

  • The greatest performance improvement is allocated when the associative memory is significantly faster then the normal page table lookup and the ht ratio is high.

  • The hit refer in the ratio between access that find a match in the associative memory and those that do not.

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