Consider a control unit design in which 42 control signals are to

SOLUTION

Concept:

In a horizontal micro-programmed control unit, one bit per control signal is required and in a vertical micro- programmed control unit, control signal is encoded for k bits as 2^k signals.

Explanation:

CASE 1:

Horizontal micro- programmed control unit (HµPU):

42 bits(for control signal)

2 bits (as 4 flag conditions)

(Next)64 – 42 – 2 = 20 bits

 

Size of control memory in words = 2²⁰

But each word contain 64 bits,

Control memory size in byte = \(\frac{{{2^{20}}\; \times\; 64}}{8} = {2^{23}} = 8\;MB\)

Maximum degree of parallelism = control signals = 42

CASE 2:

Vertical microprogrammed control unit (VµPC):

The number of locations is the same, So the next part will remain the same as 0f 20 bits.

6 bits(for control signal)

2 bits (as 4 flag conditions)

(Next)20 bits

 

Control word is of 20 + 6 + 2 = 28 bits

Control memory size in bytes = \(\frac{{{2^{20}}\; \times \;28}}{8} = {2^{20}} \times 3 = 3\;MB\)

Maximum degree of parallelism in vertical microprogrammed control unit is always 1.