Suppose that a 4M X 32 main memory is built using 1M X 8 RAM

Suppose that a 4M X 32 main memory is built using 1M X 8 RAM chips and memory is word addressable.

a)How many RAM chips are necessary? ______

b)How many RAM chips are needed for each memory word? _______

c)How many address bits are needed for each RAM chip? _______

d)How many address bits are needed for all memory?   _______

Solution

a)

The number of RAM chips =(4M * 32) / (1M * 8) = (2²² * 2⁵) / (2²⁰ * 2³) = 2⁴ = 16

b)

This question is not worded well. The only way it can make sense is to note that each chip holds one byte for each addressable item.

The design calls for two chips per 16–bit word.One chip holds the high–order byte for the word.The other chip holds the low–order byte for the word.

c)

The number of address bits are needed for each RAM chip = 20 (Since 1 M = 2^20,,so 20 address bits for each chip.

d)

The number of address bits are needed for all memory = 22 (Since 4 M = 2^22,,so 22 address bits for each chip.