4. Based on your experience in this lab, where you implemented an 8-function ALU

Question

4. Based on your experience in this lab, where you implemented an 8-function ALU with only 3 op- code bits (8 2), do you think it would always be possible to implement a K-function ALU with only n op-code bits (where K 2)? Include some explanation/thoughts with your answer. 5. When running the simulation you should have noticed sharp spikes or glitches in output signals when they were not supposed to be changing. If you study these closely, they should all occur when one or more inputs change. What is the source of these glitches? 6. Consider an ALU with 32-bit data input words. How many unique input combinations exist for each 1-input instruction (like pass A)? How many unique input combinations exist for each 2- input instruction (like ADD)? For your ALU with three (3) 1-input and five (5) 2-input instructions, how many total input combinations exist? If you wanted to test each unique input combination for all 8 instructions using a 3GHz processor executing a new instruction each clock cycle, hovw ong it would it take? Express your answer in seconds and then convert that to a more understandable unit of time (days, weeks, years, etc.). Considering your results, it is practical to test every possible input combination of all instructions for every microprocessor manufactured?

Explanation / Answer

4. Yes ,it is always possible to implement a K-Functin ALU with n-opcode bits because K=2n .Suppose that if we are implementing a 2 bit alu then 2=21 which satisfyies the expression and if we have one opcode(n) which is capable of giving 2 conditions i.e 1 or 0...in each of the condition we can perform individual operations.

5.A Glitch is caused by spurious change in signal state which does not contribute to functioning of the circuit.Glitches contribute a vast percentage in the power wastage, eliminating them would theoretically save a lot of power.There are many ways to perform the logic functions by combing various basic gates like NOT, AND, OR, etcetera. CMOS style is the most prominent style used in current technologies. The root problem is MOSFETs is that it is not an ideal switch. When a MOSFET is open it provides us with a large but not infinite resistance as we predict in an ideal and theoretical environment. When it is closed it does provide a small current due to which a small amount of current leaks and causes power dissipation because of which a glitch may occur.

6. (I)for each one input instuction it requires 32 input instructions because the data is of 32 bit and each instuction has to be executed for each op code as there are 32 op codes can be possible we can have 32 input instructions  of single bit..

(II) it requires 16 unique input combination for 2 input instruction,As the data is of 32 bits we need to perform the operations between the 2 bits like adding,subtracting,multiply etc(which requires 2 bit inputs for each instructuion)

(III)it requires 8 input combinations i.e(3 for one input and 5 for 2 input instructions).

(IV)For all 8 instruction using 3 Ghz procesor :

time period =1/f,

=(1/3) ns

T=0.33ns

The above says that inorder to generate one clock cycle it takes 0.33ns.Given that one cycle is used for executing each instructions so each instuction takes 0.33ns

therefore total time=0.33ns*8

=2.64ns

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