ISRO2014-17

Question

If each address space represents one byte of storage space, how many address lines are needed to access RAM chips arranged in a $4 \times 6$ array, where each chip is $8\;\text{K} \times 4$ bits?

• A. $13$
• B. $15$
• C. $16$
• D. $17$

Answer 1

The chips are arranged in 4x6 array, each chip is powered with 8kx4 bits.

=4x6x 8 x k x 4                     //1k=2^10
=4x6x2^3x2^10x2^2
=2^2x6x2^3x2^10x2^2=2^17x6
need 2^20 lines but storage is a type of byte not bit so, divide by 8
2^20/2^3
=2^17

so 17 lines are needed

Answer 2

Size of each Ram chip = 8K x 4 bits = 23 x 210x 22 ⇒ 215 bits = 212 bytes
Number of chips required = 6 x 4 = 24 = 5 bits
So, total number of bits required = 12 + 5 = 17 bits