70 70 votes The main memory unit with a capacity of $4$ $\text{megabytes}$ is built using $1\text{M} \times \text{1-bit}$ DRAM chips. Each DRAM chip has $1\text{K}$ rows of cells with $1\text{K}$ cells in each row. The time taken for a single refresh operation is $100\; \text{nanoseconds}$. The time required to perform one refresh operation on all the cells in the memory unit is $100$ nanoseconds $100\times 2^{10}$ nanoseconds $100\times 2^{20}$ nanoseconds $3200\times 2^{20}$ nanoseconds Digital Logic gatecse-2010 digital-logic memory-interfacing normal + – go_editor 27.7k views answer comment Share Follow Print See all 10 Comments 10 10 Comments reply Show 7 previous comments Shiva Sagar Rao commented Jan 2, 2021 reply Follow flag Similar question asked in GATE 2018: https://gateoverflow.in/204097/gate2018-23 2 2 replyShare chidambareswar23 commented Dec 5, 2025 reply Follow flag Similar question on refresh: https://gateoverflow.in/204097/gate-cse-2018-question-23 https://gateoverflow.in/3754/gate-it-2005-question-9 1 1 replyShare TanayH commented Jan 29 reply Follow flag if they ask this question in 2026 then it will be a definite proof that iit guwahati set the paper, as in only iit g did. Because this dram q is asked only 2x yet and only in IIT G papers. 1 1 replyShare Please log in or register to add a comment.
Best answer 85 85 votes There are $4\ast 8 = 32$ DRAM chips to get $4\;\text{MB}$ from $1\text{M} \times \text{1-bit}$ chips. Now, all chips can be refreshed in parallel so do all cells in a row. So, the total time for refresh will be number of rows times the refresh time $= 1\text{K} \times 100$ $= 100 \times 2^{10}$ nanoseconds Reference: http://www.downloads.reactivemicro.com/Public/Electronics/DRAM/DRAM%20Refresh.pdf Correct Answer: $B$ Arjun answered Oct 22, 2014 • edited Jun 21, 2021 by Lakshman Bhaiya Arjun comment Share Follow See all 25 Comments 25 25 Comments reply Show 22 previous comments Rgdgr8 commented Aug 4, 2021 reply Follow flag Doesn’t 1Mx1-bit imply 1M rows of 1-bit registers? Then why is 1K row and 1K column sepcified again? Can anyone clarify? 2 2 replyShare abhishekmy commented Sep 17, 2023 reply Follow flag Could somebody give the answer of this question. This is puzzling me too . It would be really be grateful 0 0 replyShare Akhilmaddili12311 commented Dec 15, 2023 reply Follow flag https://youtu.be/igPbN4_ZIs4?si=6TuZCginZngdufIs he explained it well 11 11 replyShare Please log in or register to add a comment.
1 1 vote GivenAnswer Rishabh_Chaudhari answered Jul 21 Rishabh_Chaudhari comment Share Follow 0 reply Please log in or register to add a comment.
