Unit 4 Flashcards

1
Q

What’s Von Neumann Architecture?

A

•Stored Program Concept.
•Storing programs and instructions in main memory.

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2
Q

Types of computational model?

A

•Sequential: Process an algorithm step by step
•Parallel: One task is processed by several processors
•Multi-Agent: Each task is processed by different autonomous agents(systems) to form a particular function

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3
Q

Requirements for Parallel model?

A

•An OS that supports multiple processors.
•A software program capable of distributing process between them equally.

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4
Q

How does agent work in Multi-Agent?

A

-Different Agent works in their own control(Autonomous)
-They cooperate through coordinations and negotiations.

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5
Q

What does process mean?

A

Performing a series of actions on inputs, accordingly to the given set of rules

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6
Q

What is bus?

A

A group of connection between devices in a computer (Used to connect CPU,RAM,I/O..)

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7
Q

What’s writing and reading?

A

•Writing: CPU sends data to memory to be stored at give address
•Reading: CPU retrieve data stored at given address
(both requires the data value and address)

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8
Q

What’s memory address?

A

A number that uniquely identify a memory location

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9
Q

What’s firmware and it’s function?

A

Firmware are programs permanently stored in ROM to initialize hardware components or start the OS when switch on.(Small)

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10
Q

Two programs that connects firmware to OS

A

-BIOS(Basic Input Output System)
-UEFI(Unified Extensible Firmware Interface)
(UEFI replaces BIOS)

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11
Q

Bus on CPU?

A

-A silver parallel tracks-> bus(wire connecting the chips tgt)

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12
Q

What’s cache memory?

A

Fast and expensive memory that is used to between CPU and RAM

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13
Q

What makes cache faster?

A

-Frequently used data is loaded in chunk to Cache from slower RAM.
-Cache is located between RAM and CPU so CPU access at its own speed(Faster)-> Doesn’t need to wait for data from RAM

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14
Q

What’s a bottleneck?

A

When something is working at full capacity and cannot handle more demands

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15
Q

What’s a cache miss?

A

-When the requested data for processing is not found in the cache memory

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16
Q

Why was Cache invented?

A

CPU developed much faster than RAM and
RAM couldn’t keep up with the speed which cause
limited performance by bottleneck.

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17
Q

What happens when Cache miss happen?

A

-CPU waits for the cache to reload with the correct data

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18
Q

Where is a buffer used?

A

In I/O devices between themselves and main system as they communicate with different speed

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19
Q

Why is buffer used?

A

-High speed data transfer between processor and this memory
-So CPU can continue with other tasks while I/O devices takes data from it’s buffer at slower rate.
(Chef CPU prepares dish (data) and serve at buffer and waiter(I/O) Retrieve them

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20
Q

Types of buses and their functions?

A

Data bus: carries the the value to be read or write to memory.
Address bus: carries the memory address between CPU and memory
Control bus: carries the control signal and clock pulse that determines read or write and when to do.

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21
Q

How does virtual memory work?

A

•Memory full-> Memory manager swap out least recently used data in RAM to swap area on HDD
•Requested data is swapped in to the free space on RAM

•User can manage amount of area on HDD to use as VM
•More RAM->less need of VM

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22
Q

ALU? CU? Clock?

A

Arithmetic/Logic Unit: Part of CPU that does calculation and logical operation.
Control Unit: That organises the actions of other parts of CPU.
Clock: Ticks at regular intervals and synchronise the actions of other parts of CPU.

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23
Q

Common types of registers and function ?

A

Accumulator: Holds calculations done by ALU and All I/O from CPU pass through it.
Program Counter: Holds the memory address of next instructions to be fetch
Current Instructions: Holds the instructions currently being executed.

MAR:memory address register
MDR:memory data register

24
Q

What’s Bus width and its benefits?

A

-Number of connections on a bus is bus width.
-Each connection contains 1 bit(1 or 0).
-More bus width, larger number of values can be communicated.

25
Q

What’s a register?

A

-A storage location inside CPU that holds instructions and address.
-Extremly fast access(faster than cache) and relatively small number.

26
Q

Fetch-Decode-Execute cycle?

A

Fetch: CU places memory location of next instructions on the address bus. Also sends signal to control bus requesting to read from memory. Memory receives signal and look up that memory location. It copies the data value to the data bus. CPU copies into special register(Memory buffer register)
Decode: CU analyze the contents of register and send signals to other parts telling them what to do.
Execute: The instructions is completed by CPU.

27
Q

How does Magnetic Storage Media store?

A

Actuator moves the write head on the platter
Surface with magnetic coating and change its magnetic polarity to represent 1s and 0s

28
Q

How does SSD/Flash media read or write?

A

Read:
•Control signal identify which bits to be read and apply small voltage
• electron pool is empty->Transistor on, Read as 1
•E pool full->Transistor doesn’t turn on, Read as 0.
•Control signals are changed to read other bits.

Write:
•Control signal identify which bits to be written.
•Apply high voltage to pull electrons to the pools of transistors, recoding 1s and 0s.
•Erasing also apply higher V to remove electrons.

**Both Read/Write cause transistor to break down slowly.

29
Q

How does Optical media read and write?

A

Write:
•Write laser heats the recording material to creates pits.(Slow because time for heating and cooling for each bit.)

Read:
•Disk spins->Ensure all data can be read
•Tracking mechanism moves read laser head into correct posion over disk.
•Laser is shine on the the disk and reflected back to light sensor.
•Signals from sensor are translated as 1s and 0s.

30
Q

What’s paging?

A

Moving programs from RAM to disk and back again when needed.(When ram full)

31
Q

What is access time in HDD?

A

Seek time+Latency

32
Q

Disk Thrashing

A

Very high rate of HDD access

33
Q

Factors that affect the performance of CPU?

A

•Size of Cache
•Bus width
•Clock speed
•Number of processor cores

34
Q

Disadvantages to using Virtual Memory?

A

•Slower read/write speed (HDD isn’t made for accessing small piece at a time.)
•Significant performance drop
•Slow down the execution of programs (Disk Thrashing; constantly swap infos)

35
Q

What is a clock speed?

A

The rate at which instructions are processed by CPU

36
Q

Disadvantages of higher clock speed?

A

•Instructions are processed by transistor->Rate of operation is limited
•It generates tons of heat.(More clock speed ->More heat)
(Heat sink & Fan prevent CPU from melting)(Limited to rate of cooling)
•Need liquid nitrogen to cool 9GHz Processor

37
Q

Pros of Multcore processors?

A
  • If task isn’t sequential,
    •Wort tgt on same program(Parallel processing)
    •work on different programs at the same time(multi tasking)
38
Q

What does cache stores in it? And how many levels are there rank them by speed(check first)

A

Data caches: Have to be read and written to.
Instructions caches: Only read.

L1(Smallest,Fastest)>L2>L3

39
Q

Structure of Caches?

A

In multicores,
•Have own L1 and L2 but share L3.
•L1 has own L1 D and L1 I.
•Larger cache ->Greater probability of requested I/D in a cache(No cache miss, Doesn’t need RAM to be accessed. Speed up processing)

40
Q

How does HDD read?

A

•Arm moves across the right track(Seek time)
•Required sector comes under the head (Latency)
•Surface behaving like a magnet causes a tiny current in the head
•Disk controller translates it into 1s and 0s
{CIRCULAR}

41
Q

Structure of HDD?

A

•Stack of disk(Platters) with magnetic coating
•Magnetic recording head on the end of an arm float 1/10⁶ cm.
•Disk spins at 110 km/h
•Stored on sector , smaller parts of track

42
Q

Details of SSD?

A

SSD uses NAND flash chips, made of special kinds of transistors that can trap electrons in a pool.

43
Q

Differentiation between SAN and NAS?

A

•Network-Attached Storage is a single device that serves file over Ethernet.(can directly connect to HDD)(Cheaper)
•Storage Area Network is a networks of multiple devices.(connect to several servers)

44
Q

What is virtualization? Give an example.

A

-Hiding true physical nature of computing resource.(making it look different; Simplify)

Eg.
Access to cloud -> Access as tho to single virtual hard drive but actual storage spread across the world. Software deal with details where each part of file located.

45
Q

Advantages of cloud storage?

A

•Can access from anywhere with internet.
•Doesn’t need to transfer data when device change
•Data is securely backed up

46
Q

What’s IoT? With examples

A

Internet of things: Interconnection of digital devices embedded in everyday objects

Eg. Printer auto ordering toner when it’s low

47
Q

Why is assembly language a low level language?

A

Because programmer is working at the lowest level of details( level of CPU hardware itself)

48
Q

Why is Assembly easier than machine code?

A

Each instruction is written in short, memorable keywords(Mnemonic)

49
Q

3 reasons why assembly language is challenging?

A

•Limited instructions available.(every task has to be built from smallest steps)

•Have to manage all your data. Decide and manage
°where data is stored in memory
°How to represent the data(No int,str,real

•Difficult debugging.(bug when run->Machin crash and reboot)

50
Q

Assembly pros and usage?

A

-Very small
-Very fast
-Directly control I/O hardware.

Usage: Hardware drivers and program running on embedded systems

51
Q

What is scheduling?

A

-Give each program exclusive use CPU for a short time before switching to next program.(create illusions of several app running simultaneously)

52
Q

Why program code/source code need to be translated before executed by computer?

A

-High level language use natural language commands(easy for human to understand) and Computer only understands machine code where binary are used.

53
Q

OS jobs

A

•Managing I/O
•Managing files & the directory structure
•Share access to Hardware
-Among diff programa
-Among diff users
•Scheduling
•Paging

54
Q

States the directions of each bus

A

Address bus: Unidirectional
Control/Data: Bidirectional

55
Q

Purpose of user management?

A

•Provide access to the device by controlling who can log on to the device by authentication(Username/Password)