Nanoprogramming:

•  Second compromise: nanoprogramming
•  it use a 2-level control storage organization
•  Top level is a vertical format memory
•  Output of the top level memory process the address register of the bottom (nano- level) memory
•  Nanomemory uses the horizontal format
•  Generate the real control signal outputs
•  The benefit to this method is significant saving in control memory size (bits)
•  Disadvantage is more difficulty and slower operation (doing 2 memory accesses for each microinstruction)

Nano programmed machine

• Instance : Assume that a system is being designed with 200 control points and 2048 microinstructions

o   Suppose that only 256 different combinations of control points are ever used

o   A single-level control memory would need 2048x200=409,600 storage bits

•   A nano programmed system would utilize
•   Microstore of size 2048x8=16k
•   Nanostore of size 256x200=51200
•   Total size = 67,584 storage bits
•   Nano programming has been used in many CISC microprocessors