Electronics Engineering (ELEX) Board Practice Exam

To connect a 90 GB memory to a microprocessor, how many address lines are required at a minimum?

1. 32

2. 36

3. 37

4. 40

The correct answer is: 37

To determine the minimum number of address lines required to connect a 90 GB memory to a microprocessor, we need to calculate how many unique addresses can be generated with a given number of address lines. The total number of addresses that can be accessed is given by the formula \(2^n\), where \(n\) is the number of address lines. First, we convert 90 GB to bytes, knowing that 1 GB equals \(2^{30}\) bytes: \[ 90 \, \text{GB} = 90 \times 2^{30} \, \text{bytes} = 90 \times 1,073,741,824 \, \text{bytes} = 96,262,448,640 \, \text{bytes} \] Next, to find how many address lines we need, we need to determine the smallest \(n\) such that \[ 2^n \geq 96,262,448,640 \] Calculating the powers of two: - \(2^{36} = 68,719,476,736\) (which is less than 90 GB) - \(2^{37} = 137,438,