Processing Unit Design - Fundamentals of Computer Organization and Architecture - page 105

(b) Three memory addresses in a machine with 64 KB of main memory?
2. Show the micro-operations of the load, store, and jump instructions using:
(a) One-bus system
(b) Two-bus system
(c) Three-bus system
3. Add control signals to all the tables in Section 5.4.
4. Data movement within the CPU can be performed in several different
ways. Contrast the following methods in terms of their advantages and
disadvantages:
(a) Dedicated connections
(b) One-bus datapath
(c) Two-bus datapath
(d) Three-bus datapath
5. Find a method of encoding the microinstructions described by the following
table so that the minimum number of control bits is used and all inherent
parallelism among the microoperations is preserved.

Microinstruction Control signals activated

I 1 a, b, c, d, e

I 2 a, d, f, g

I 3 b, h

I 4 c

I 5 c, e, g, i

I 6 a, h, j

6. Suppose that the instruction set of a machine has three instructions: Inst-1,
Inst-2, and Inst-3; and A, B, C, D, E, F, G, and H are the control lines.
The following table shows the control lines that should be activated for
the three instructions at the three steps T0, T1, and T2.

Step Inst-1 Inst-2 Inst-3

T0 D, B, E F, H, G E, H

T1 C, A, H G D, A, C

T2 G, C B, C

(a) Hardwired approach:
(i) Write Boolean expressions for all the control lines A-G.
(ii) Draw the logic circuit for each control line.
(b) Microprogramming approach:
(i) Assuming a horizontal representation, write down the micropro-
gram for instructions Inst-1. Indicate the microinstruction size.