GATE CS 2018 Set 1 — Question 33
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Computer Organization & Architecture → Memory Hierarchy & Cache → Memory Technologies (SRAM, DRAM, ROM)
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Question
A -bit wide main memory unit with a capacity of is built using DRAM chips. The number of rows of memory cells in the DRAM chip is . The time taken to perform one refresh operation is . The refresh period is . The percentage (rounded to the closest integer) of the time available for performing the memory read/write operations in the main memory unit is __________.
Correct answer
59 to 60
Solution
To find the percentage of time available for memory read/write operations, we first calculate the total time spent on refreshing the DRAM rows within one refresh period.
Converting this to milliseconds ():
1.Identify the number of rows to be refreshed:
The number of rows in each DRAM chip is given as .2.Calculate the total refresh time:
Each refresh operation takes . The total time required to refresh all rows is:Converting this to milliseconds ():
3.Calculate the time available for read/write operations:
The refresh period is . The time available for normal operations is the total period minus the time spent refreshing:4.Calculate the percentage of available time:
5.Rounding to the closest integer:
Rounding to the nearest integer gives .Continue learning with Success Tracker
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