Study On The Instruction Cycle Computer Science Essay


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In order to write a value, data's address to be written is placed in MAR and the value or data is kept in data bus. Address bus designates towards the address of source or destination of data on data bus. Control bus controls the access of data and address lines. The access limitations are place in control lines

Problem 2.9:

ENIAC has a major drawback that it has to be programmed manually setting the switches and plugging and unplugging the cables.

If multiple vacuum tubes are in ON and OFF state simultaneously, the above mentioned working process of ENIAC makes it "wasteful" as there is no program storage concept existed before World War II.

Using 10 vacuum tubes we can represent 29 integer values.

Problem 3.3:

For 32- bit microprocessor

24=16 bit Opcode and 228 =268M words can be directly accessed

1) 32 - bit local address bus and 16- bit local data bus:

We can access a 4 byte word with the above lengths of busses

2) 16 - bit local address bus and 16- bit local data bus:

We can only access 1 byte word with the above busses

For instruction register we need an 8-bit Opcode i.e. 28 bits and program counter contains the next executable instruction so the required buts depends upon the incoming instruction.

Problem 3.11:

a. With a clocking frequency of 10 MHz, the clock period is 10-9 s = 100 ns. The length of the memory read cycle is 300 ns.

b. The Read signal begins to fall at 75 ns from the beginning of the third clock cycle (middle of the second half of T3). Thus, memory must place the data on the bus no later than 55 ns from the beginning of T3.

Problem 3.12:

a. The clock period is 125 ns. Therefore, two clock cycles required to insert.

b. From Figure 3.19, the Read signal begins to rise early in T2. To insert two clock

cycles, the Ready line can be put in low at the beginning of T2 and kept low for

250 ns.

Problem 3.13:

a. A 5 MHz clock corresponds to a clock period of 200 ns. Therefore, the Write signal has a duration of 150 ns.

b. The data remain valid for 150 + 20 = 170 ns.

c. One wait state.

Problem 4.10:

Tag Set Word

10 2 4

Address length=(s+w) bits =12+4

Number of addressable units=2s+w = 216

Block size=line size=2w=24

Number of blocks in main memory=2s=212

Number of lines in set=k

Number of sets=v=2d=22

Number of lines in cache=k*v=k*2d

Size of tag= (s-d) =12-2=10

Problem 4.15:

Nested for loop and assignment operator is example of spatial locality in code. reference to first instruction is immediately followed by the second instruction

For loop is example of temporal locality. The ten access to a[i] within the inner loop occurring after short intervals.

Problem 4.21:

a. 2.5 ns are required to determine that a cache miss occurs. The required line is read into the cache. Then an additional 2.5 ns are needed to read the requested word.

Tmiss = 2.5 + 50 + (15)(5) + 2.5 = 130 ns

b. The value Tmiss from part (a) is equivalent to the quantity (T1 + T2) in Equation

(4.1). Under the initial conditions, using Equation (4.1), the average access time is

Ts = H Ã- T1 + (1 - H) Ã- (T1 + T2) = (0.95)(2.5) + (0.05)(130) = 8.875 ns

Under the revised scheme, we have:

Tmiss = 2.5 + 50 + (31) (5) + 2.5 = 210 ns


Ts = H Ã- T1 + (1 - H) Ã- (T1 + T2) = (0.97) (2.5) + (0.03) (210) = 8.725 ns

Section B:

Write a program to multiply 2000 to numbers from 1 to 1001 and store the results in memory locations

MEM A; loading to memory from accumulator

MEM B; loading to memory from accumulator

LDR 2000; load 2000 to it

STR A; storing to mem location A

LDR 1000; load 1000 to it

STR B; storing to mem location B


STR B; storing to mem location B

STR IR; storing to instruction register


LDR A; loading to mem location A


STR A; storing to mem location A


DEC #1;

STR IR; storing to instruction register



END 1;

LDR A; loading to mem location A

LDR B; loading to mem location A

DEC #1;



E END 2;

Divide 98000 by numbers from 802 and 55 and then store the results

MEM A, B,C; reserving memory location in memory

LDR #98000; loading 98000 to accumulator

STR A; storing into mem loc A

LDR #802; loading 802 to accumulator

STR B; storing to mem loc B

LDR #0; loading 0 to accumulator

STR IR; storing to instruction register

STR C; storing to mem loc C


LDR A; loading to A



INC #1;



E1: END;


LDR A; loading to A

SUB #55

STR A; storing to mem loc A

LDR C; loading to C

ADD #1;




E2: END;

Section C:

List and describe computers starting from 1950s. Research computers for the past 50 years. Identify the different kinds of computer existed. Identify their major characteristics.

First Generation Computers (1941-1956):

World War II provided a way towards the development in computers. The first computer was ENIAC containing 18,000 vacuum tubes and 7000 resistors. Though it was designed for war purpose but it was used as a general purpose computer. It was modified with a program and data storage concept and EDVAC was born.

Universal Automatic Computer (UNIVAC I) was created in 1951. It was the property of US census beuru and General Electric collectively. Its perfectness can be judge as; it predicted the winner of 1952's presidential elections.

In first generation computers, the operating instructions or programs were particularly built for the specific task for which computer was manufactured. The computers can only understand the machine language. It became extremely difficult when there were some malfunctions. First Generation computers used Vacuum tubes and magnetic drums (for data storage).The first electronic computer is created in Japan by Hideo Yamachito.

1943: Colossus was an electronic computer built in Britain at the end 1943 and designed to crack the German coding system

1945: "ENIAC" the first digital computer was invented.

1950: The Pilot ACE computer, with 800 vacuum tubes, and mercury delay lines for its main memory, became operational on May 10, 1950 at the National Physical Laboratory near London.

1950: Transistors were introduced by John Bardeen and William Shockley from Bell Labs

1951: Universal Automatic Computer (UNIVAC I) came into existence.

1951: The first commercial computer, named the "First Ferranti MARK I," became functional at the Manchester University.

1955: MIT built the "Whirlwind" for the U.S. Air Force invented RAM in the process.

Second Generation Computers (1956-1963):

The instructions (program) could be stored inside the computer's memory. High-level languages such as COBOL (Common Business-Oriented Language) and FORTRAN (Formula Translator) were used, and they are still used for some applications nowadays.

1956: At MIT, researchers began experimentation on direct keyboard input on computers, a forerunner of today's normal mode of operation.

1958: integrated circuit were invented and brought a revolution in computer world

1959:  Robert Noyce's practical integrated circuit, invented at Fairchild Camera and Instrument Corp., allowed printing of conducting channels directly on the silicon surface.        

1959: IBM's 7000 series mainframes were the company's first transistorized computers

1960: Common Business Oriented Language (COBOL) was developed by a team drawn from several computer manufacturers and the Pentagon.

Third Generation Computers (1964-1971):

The operating systems allowed the machines to run many different applications and IC began to use in computers

1964: Thomas Kurtz and John Kemeny created BASIC, an easy-to-learn programming language, for their students at Dartmouth College

1965: Digital Equipment Corp. introduced the PDP-8, the first commercially successful minicomputer

1966: Hewlett-Packard entered the general purpose computer business with its HP-2115 for computation, offering a computational power formerly found only in much larger computers.

1968: The Apollo Guidance Computer made its debut orbiting the Earth on Apollo 7

1969: AT&T Bell Laboratories programmers Kenneth Thompson and Dennis Ritchie developed the UNIX operating system on a spare DEC minicomputer.

Fourth Generation Computers (1971-Present):

The Size started to go down with the improvement in the integrated circuits. Hence a large number of components are made their space over a small IC chip

1971: microchips and floppy disks were invented making another step towards ease of man.

Intel 4004 chip was designed and IC took a step ahead by locating all the components of a computer (central processing unit, memory, and input and output controls) on a minuscule chip."

1975: Birth of Microsoft; a step ahead towards the creation of windows.

1981: IBM introduced personal computers for home and office use.

1984: Apple Computers developed the Graphical User Interface (GUI), a gateway to modern computers and step to windows operating system

1990: Computers became easily accessible to a university student

Macintosh introduced Graphic User Interface in which the users didn't' have to type instructions but could use Mouse for the purpose.

The continued improvement allowed the networking of computers for the sharing of data. Local Area Network (LAN) and Wide Area Network (WAN) were potential benefits, in that they could be implemented in corporations and everybody could share data over it. Soon the internet and World Wide Web appeared on the computer scene and fomented the Hi-Tech revolution of 90's.


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