Example
  If cpu capable of address 1MB memory, and memory chips come in 64K
  units, how many memory chips are needed?

  1MB = 1*2^20 bytes,  64K = 64*1K = 2^6*2^10 = 2^16 bytes/chip

  (2^20 bytes)/(2^16 bytes/chip) = 2^(20-16) = 2^4 chips = 16 chips.

  How many address lines are on each chip?  16

  A decoder will be needed to select the appropriate chip, how 
  many select lines are needed?  4^2 = 16   4