DRAM refresh operation

Question

how we will come to know that wt overhead.  means here??

Comments

See here:

https://en.wikipedia.org/wiki/Memory_refresh

RAM part is in syllabus?

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sir they have taken MHz as $10^8$. any concept or simple mistake they have done. and sir plz confirm whether ram is in syllabus or not ,

Answer 1

Clock Rate is 133 MHz, it means 133 x 10⁶ Clock Cycle in 1 Sec.

therefore, 1 Clock Cycle= $\frac{1}{133 \ast 10^{6}} second$

4 Clock Cycle will take $4 \ast \frac{1}{133 \ast 10^{6}} second$

Each row will take 4 Clock Cycle and we have 8K rows, so refresh time= $2^{13}\ast 4 \ast \frac{1}{133 \ast 10^{6}} sec=0.246 msec$

Overhead=$(0.246\div 64)\ast 100 = 0.384$

Memory refresh cycle is the overhead as in dynamic RAM during a refresh cycle the memory module cannot initiate a read or write cycle until the refresh cycle has been completed. so no prductive work during refresh cycle. Hence Overhead.