Suppose you want to build a memory with 4 byte words with a capacity of 221bits. What is type of decoder required if the memory is built using 2K x 8 RAM chips?
(A) 5 to 32
(B) 6 to 64
(C) 4 to 64
(D) 7 to 128


Answer: (A)

Explanation: Memory of 221bits is to be built using 4 byte words. So, number of 4-byte words memory should have

= 221/(4*8) = 216 words

Given RAM chips are of size = 2K x 8
Memory to be built using these RAM chips = 216
Required RAM chips = (216 x 32) / (2K x 8) = 32 x 4
So, the arrangement of these RAM chips should contain 32 rows each with 4 columns.

A Decoder is required to select a specific row and multiplexer is required to select a particular column. 5 to 32 Decoder will be required to select the desired row.

SO, option (A) is correct.


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  • Last Updated : 19 Nov, 2018

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