Chapter 5 Computing Components Components Circuits Gates Transistors Yet another layer of abstraction!
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Chapter 5
Computing Components
Components
Circuits
Gates
Transistors
Yet another layer of
abstraction!
Multipliers
2
When referring to computer memory, mega does not mean one million! (but it’s still close to that)
3
Decimal vs. binary multipliers
1000 = 103 1,000,000 = 106 1,000,000,000 = 109
1024 = 210 1024*1024 = 220 1024*1024*1024 = 230
Rule:
For memory capacities, the multipliers are binary, for
everything else (speed, frequency, pixels, etc.) they
are decimal
k vs. K
4
Decimal vs. binary multipliers
examples
What is the meaning of:
• 500 GB hard-disk
• 54 Mbps wireless Ethernet
• 3 GB of RAM
• 8 Mega-pixel camera
• 3.2 GHz CPU
QUIZ
1. How many bytes are in the memory pictured? 2. Express the result using the appropriate multiplier.
The Fetch-Execute Cycle
6
According to the CPU’s
machine language
Secondary Storage Devices
Name a few …
Why is it necessary to have secondary storage devices?
7
Secondary Storage Devices Why is it necessary to have them?
• Saving data when computer is off
• Volume …
– “Mass storage”
• Portability …
• Reliability (backups) …
• Modularity (add as you go) …
8
QUIZ: HDD
A HDD has 512 Bytes/sector, 256 sectors/track, and 10 platters. The diameter of each platter is 10 cm, and each track is 1 mm wide. Calculate the total capacity of the drive in MB.
Use binary Mega!
QUIZ: HDD
A HDD has 512 Bytes/sector, 256 sectors/track, and 10 platters. The diameter of each platter is 10 cm, and each track is 1 mm wide. Calculate the total capacity of the drive in MB.
Use binary Mega! 250 MB
Seek time
Time it takes for read/write head to be over right track
Latency
Time it takes for sector to be in position
Access time = Seek time + latency
Transfer rate (e.g. 100 MB/s)
11
QUIZ1: HDD
The spindle of a HDD rotates at 7200 RPM.
Calculate the average latency.
12
QUIZ1: HDD
The spindle of a HDD rotates at 7200 RPM.
Calculate the average latency.
4.16 ms
What are the minimum and maximum possible latencies?
13
QUIZ2: HDD
A file is on the HDD, on 15 consecutive blocks of the same track. Each block stores 4 KB.
The average seek time is 10 ms, and the average latency is 5 ms.
Once the first block is under the head, data is transferred at a rate of 50 MB/s.
Calculate the total time needed to transfer the file.
14
QUIZ2: HDD
A file is on the HDD, on 15 consecutive blocks of the same track. Each block stores 4 KB.
The average seek time is 10 ms, and the average latency is 5 ms.
Once the first block is under the head, data is transferred at a rate of 50 MB/s.
Calculate the total time needed to transfer the file. 17.9 ms 15
QUIZ Pipelining
A computer pipeline has 3 stages, as shown above.
Each stage takes 10 ms to execute, and each instruction must go sequentially through all 3 stages.
A program has 1000 instructions. Calculate how long it takes to run it:
• without pipelining
• with pipelining 16
QUIZ Pipelining
Can you come up with a formula for N stages?
(Assume the # of instructions is large)
17
Chapter review questions
• Read an ad for a computer and understand the jargon
• List the components and their function in a von Neumann machine
• Describe the fetch-decode-execute cycle of the von Neumann machine
18
Chapter review questions
• Describe how computer memory is organized and accessed
• Name and describe different auxiliary storage devices
• Define three alternative parallel computer configurations
19
20
Ethical Issues
Computer Hoaxes and Scams:
What is the principal difference between a hoax and a scam?
What are the most common complaints of Internet users about computer scams and hoaxes?
What are the most serious crimes perpetrated on the Web?
Why is it so difficult to police these schemes?
QUIZ
The previous version of PEP, PEP/7, could use only 12 bits for memory addresses.
How many Bytes of memory could PEP/7 address?
21
Some Sample Instructions
22
Sample Instructions
23
What does this instruction mean?
Sample Instructions
24
What does this instruction mean?
Sample Instructions
25
What do these instructions mean?
Sample Instructions
26
What do these instructions mean?
27
Sample Instructions
What does this instruction mean?
Why is there only one on this page?
28
Sample Instructions
What do these instructions mean?
Problem 16 / 189
29
The PEP/8 memory has the following contents:
0001 A2
0002 11
0003 00
0004 FF
What are the contents of reg. A after this instruction
is executed:
C1 00 01
30
0001 A2
0002 11
0003 00
0004 FF
Instruction
executed:
C1 00 01
31
Steps for executing a machine-language
program
Loader
Program
in
memory Execute
32
Steps for executing an assembly-language program
Loader
Program
in
memory Execute
Pep/8 Assembly Language
33
QUIZ: Write this program in assembly
34 EoL
Assembler directives, a.k.a. pseudo-ops
35
What is the difference between
operations and pseudo operations?
36
QUIZ: Change the program so it adds up four numbers
Food for thought: What to do it we need to add up 100 numbers? 1000?
37
Decision Making
38
BR Set PC to operand unconditionally
BRLT i Set PC to operand if A < 0
BREQ I Set PC to operand if A = 0
QUIZ: Would the program still work if the negMsg block were placed after the main program instead of before?
39
main: LDA sum,d
…
BRLT negMsg
STA sum,d
DECO sum,d
finish: STOP
negMsg: CHARO 0x0045,i
BR finish
QUIZ: Change the program so it prints 'Z' (for zero) if the sum is zero, and prints the actual sum if nonzero.
40
main: LDA sum,d
…
BRLT negMsg
STA sum,d
DECO sum,d
finish: STOP
negMsg: CHARO 0x0045,i
BR finish
QUIZ on Decision Making
Write a PEP assembly program that reads in a character, and then outputs ‘A’ if the character was A, or ‘not A’ otherwise.
(ASCII code for A is 41 hex)
41
Chapter Review Questions
• List the operations that a computer can perform
• Describe the important features of the Pep/8 virtual machine
• Distinguish between immediate addressing mode and direct addressing mode
• Write a simple machine-language program
• Distinguish between machine language and assembly language
42
Chapter Review Questions
• Describe the steps in creating and running an assembly-language program
• Write a simple program in assembly program
• Distinguish between instructions to the assembler and instructions to be translated
• Distinguish between following an algorithm and developing one
• Describe the pseudocode constructs used in expressing an algorithm
43
Chapter Review Questions
• Use pseudocode to express and algorithm
• Describe two approaches to testing
• Design and implement a test plan for a simple assembly-language program
44
Review problems for Ch.6: --Rewrite the loop program with the decision part at the beginning of the loop (use the red flowchart) --End of chapter 15, 22, 23, 37
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