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Memory Management and Virtual Memory

GATE CSE 2014 Set 3 · Q33

NAT2 marksEasy

Time

Consider a paging hardware with a TLB. Assume that the entire page table and all the pages are in the physical memory. It takes 10 milliseconds to search the TLB and 80 milliseconds to access the physical memory. If the TLB hit ratio is 0.6, the effective memory access time (in milliseconds) is ________.

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Solution

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Official answer: 122

Memory Management and Virtual Memory

Given:

  • TLB search time (tTLBt_{TLB}) = 10 ms10\text{ ms}

  • Physical memory access time (tmt_m) = 80 ms80\text{ ms}

  • TLB hit ratio (hh) = 0.60.6

  • TLB miss ratio (1−h1 - h) = 0.40.4

When a TLB hit occurs:

Timehit=tTLB+tm=10+80=90 ms\text{Time}_{\text{hit}} = t_{TLB} + t_m = 10 + 80 = 90\text{ ms}

When a TLB miss occurs:

Timemiss=tTLB+2×tm=10+80+80=170 ms\text{Time}_{\text{miss}} = t_{TLB} + 2 \times t_m = 10 + 80 + 80 = 170\text{ ms}

(one memory access to fetch the page table entry, and one memory access to fetch the target frame/data).

Effective Memory Access Time (EMATEMAT):

EMAT=h×Timehit+(1−h)×TimemissEMAT = h \times \text{Time}_{\text{hit}} + (1 - h) \times \text{Time}_{\text{miss}}
EMAT=0.6×90+0.4×170=54+68=122 msEMAT = 0.6 \times 90 + 0.4 \times 170 = 54 + 68 = 122\text{ ms}

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This Memory Management and Virtual Memory previous year question is Q33 of the GATE CSE 2014 Set 3 paper. Find more GATE CSE PYQs on Memory Management and Virtual Memory in Operating Systems, or browse all GATE CSE PYQs.

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Memory Management and Virtual Memory in GATE CSE

Memory Management and Virtual Memory has 32 GATE CSE PYQs across 22 papers from 2011 to 2026. 15 of them are 2-mark NAT questions like this one, and GATE CSE 2014 Set 3 has 2.

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GateAI solution cardGATE CSE 2014 Set 3 · Q33 · NAT

Consider a paging hardware with a TLB. Assume that the entire page table and all the pages are in the physical memory. It takes 10 milliseconds to search the TLB and 80 milliseconds to access the physical memory. If the TLB hit ratio is 0.6, the effective memory access time (in milliseconds) is …

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