How many bits are required to address a 8G X 64 main memory

How many bits are required to address a 8G X 64 main memory if

a)Main memory is byte addressable?

b) Main memory is word addressable?

Solution

1G= 2⁴⁰. So taking this in the calculation we can have.

a) Byte addressable: 8G x 64 = 2³ x 2⁴⁰ x 2³ (8 bytes, or 64 bits) = 2⁴⁶, or 46 bits

b) Word addressable: 8G x 64 = 2³ x 2⁴⁰ x 2² (4 word, or 64 bits) = 2⁴⁵, or 45 bits