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Suppose you want to build a memory with $4$ byte words and a capacity of $2^{21}$ bits. What is type of decoder required if the memory is built using $2K \times$ $8$ $\text{RAM}$ chips?

  1. $\text{5 to 32}$
  2. $\text{6 to 64}$
  3. $\text{4 to 16}$
  4. $\text{7 to 128}$
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Capacity of memory = 2^21 bit

So, Capacity of memory in Byte will be = 2^21/2^3 = 2^18 bytes

Word size of 4 Byte is given, from this we can calculate no. of words in memory = 2^18/ 2^2 = 2^16 words.

RAM chip size capacity is = 2K X 8 (means 8 bit word can be store in one cell of RAM), therefore, RAM capacity = 2^11 words.

No. of decoder line req. = 2^16/2^11 = 2^5 = 32
Answer:

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