##### How many RAM chips needed & what is the size of decoder used?

How many 256 X 4 RAM chips are required to organize a memory of capacity 32KB ? What is the size of decoder required in this implementation to select a row of chip?

Options :

(a) 128 , 7 X 128

(b) 256 , 7 X 128

(c) 512 , 7 X 128

(d) 256 , 8 X 256.

Gagan Batra
14 Mar 2016 11:33 pm

Option D should be correct.

target size = 32KB = 32K x 8 (1 Byte = 8 bits) = 215 x 8 bits

basic size = 256 x 4 = 28 x 4 bits

No of chips = target size/ basic size = 27 x 2 = 256

Size of decoder can be calculated from the row chips of basic size = 8 x 28 = 8 x 256

Note - If basic size is 2M x N then size of decoder is M x 2M

Jitendra Verma
14 Mar 2016 11:48 pm

Gagan Batra
14 Mar 2016 11:53 pm

Jitendra Verma
14 Mar 2016 11:57 pm

No of chips=32K*8/256*4=256

1 chip 4 bits

And for byte (8 bits) we need 2 chips in row

Total no of rows =128

So 7:128 decoder is required to select a row

Charan
27 Dec 2018 11:59 pm
Where is it written that it is Byte addressable? In this way we can take 16 bits for one row.
khdijah
17 May 2017 11:21 am