Coa

Front 1

What is principal of locality

Back 1

Locality of space state that codes that are close together is likely to be accessed together

Locality of time is recently used data is likely to be executed again

Front 2

3 type of Cache replacement policy

Back 2

Least recently used (LRU)

Fifo(first in first out)

Random replacement policy

Front 3

Wad is LRU

Back 3

Least recently used data is being evicted, disadvantage is the LRU need to maintain history of the block which slows down the cache

Front 4

What is FIFO

Back 4

First in first out policy, the data that is in the cache the longest will be evicted first

Front 5

What is random replacement policy

Back 5

Random block is being replace by the new block thus it nv thrashes

Front 6

What is cache thrashing

Back 6

Cache blocks being replace frequently

Front 7

What is cache coherency

Back 7

Cache coherency occurs when the cpu writes into the cache but haven't update the main memory

Front 8

Types of write policy

Back 8

Write through policy

Write back policy

Front 9

What is write back policy

Back 9

Write back policy only update the memory when the block is selected for replacement

Front 10

What is write through policy

Back 10

Write through policy update both cache n memory simultaneously on every write (no cache coherence issue )

Front 11

What is Cache hit

Back 11

Data is found in the cache

Front 12

What is cache miss

Back 12

Data nt found in the cache

Front 13

What is cache hit rate

Back 13

The percentage of time data being found in the cache

Front 14

What is cache miss rate

Back 14

The percentage of time data not found in the cache

Front 15

Formula for cache effective access time

Back 15

EAT= Hit rate * cache access time + (1-hit rate) *(cache access time +main memory access time)

Front 16

What is virtual memory

Back 16

Is a technique used to map the virtual memory address to the physical memory address

Front 17

Advantage of virtual memory

Back 17

-Allows system to run programs tat are larger than the size of main memory

Front 18

What is translation lookaside buffer (TLB)

Back 18

Page table is located at the main memory thus access is slow, thus a page cache table (TLB) is used to store the recently page lookout value to speed up the page translation process

Front 19

Another approach to virtual memory

Back 19

Segmentation

Front 20

What is segmentation

Back 20

Instead of dividing the virtual memory into equal size, it divide the virtual memory to variable length segment and access the data through the segment table

Front 21

What is memory fragmentation

Back 21

Memory fragmentation occurs when there are small cluster of unusable memory address being created, paging n segmentation can cause fragmentation

Front 22

Wat subject to internal fragmentation. WHY

Back 22

Paging, a process may not necessary need the entire range of address for a page, thus creating unused fragment of memory

Front 23

What is seek time

Back 23

It is the time taken for the head to move to the correct track

Front 24

What is rotational delay (Tr)

Back 24

Is the time taken to rotate the head to the start position of the sector

Front 25

What is access time (Tr + Ts)

Back 25

Is the time taken from the request to the time the head is in position

Front 26

What is transfer time (Tt)

Back 26

Is the time taken to transfer the required data afterthe head is in position

Front 27

Formula for T(rav)

Back 27

0.5/RPS second

Front 28

Sample ques

Back 28

Front 29

What is SSD make up off

Back 29

Is made up of NAND N NOR FLASH

Is more expensive than Magnetic hard disk

Limited erase cycle

Front 30

Advantage of HDD

Back 30

Lower cost per bit

Almost infinite erasure cycle

Front 31

Disadvantage of HDD

Back 31

Consist of moving part,prone to data crashing if HDD is shaken or dropped

Heavier and larger physical profile

Slow transfer rate

Front 32

Disadvantage of virtual memory

Back 32

Take longer access time

Front 33

3 Advantage of SSD

Back 33

Fast transfer rate

Lighter, occupy less space

More robust to movement (immune to vibration)

Front 34

Disadvantage of SSD

Back 34

Finite erasure cycle

Higher cost per bit

Front 35

Two addressing scheme for HDD

Back 35

Cylinder - head sector(CHS ) and logical block addressing(LBA)

Front 36

What are the technique use to extend the life of the SSD

Back 36

Wear LEVELLING Technique

And use external ram as a buffer to minimise the number of write to the flash in SSD

Front 37

What is wear levelling technique

Back 37

It is to use to extend the SSD life by distributing the data and erase/write cycle evenly on the entire disk

Front 38

Formula for probability tat a unit survive

Back 38

Front 39

Explain Raid level 0

Back 39

It has zero redundancy and have the best performance. It need minimum 2 disk and data is strip as block across all disk But it has no fault tolerance thus lack of reliability

Front 40

Explain Raid level 1

Back 40

It is a mirrored disks

There's 100% redundancy, each data is written identically to each disk. Write through is slower as every time u write data it will update all the disk

Need minimum 2 disk

Front 41

What is the advantage of raid level 1

Back 41

Faster read operations

Disk recovery is simple, swap fault disk and remirror

Front 42

What is the disadvantage of raid 1

Back 42

Expensive

Write through is slower as need to update every drive

Front 43

Explain Raid level 5

Back 43

It is a block level stripping with single distributed parity, data on a single failed drive can be recover through the parity info and surviving data. Is commonly use in network server

Front 44

Explain Raid 6

Back 44

Is a block level stripping with double distributedparity

It can recover from multiple disk failure

Front 45

Advantage of raid 6

Back 45

Higher data availability

Front 46

Disadvantage of raid 6

Back 46

Write operation will be slower

Front 47

Explain Raid 10

Back 47

Is a combination of raid 1 and 0,

It will be more expensive as compared to raid 1 n 0

Front 48

Why raid is used

Back 48

To improve access time and store the data and reserve redundancy so when one of the hard disk fail the data will not be lost

Front 49

3 type of pipelining conflict

Back 49

Resource conflict

Data dependencies

Branch statement

Front 50

What is common pitfall

Back 50

Common pitfall is to assume tat we can use each metric separately to measure performance

Front 51

Types of performance metric

Back 51

Clock frequency

Millions of instruction per second (MIPS )

power consumption

Execution time (seconds, millisecond

Front 52

What is the key advantage tat synthetic benchmarks& EEMBC benchmarks have over synthetic benchmark like linpack and whetstone

Back 52

There's third party validation of result

Front 53

What is standard performance evaluation spec(spec?) benchmarks

Back 53

It is formed to address the need for objective benchmarks

Users run the benchmark and submit the result to spec for review. Spec will then publish the review result on the website

Front 54

What is embedded microprocessor benchmark consortium (EEMBC)

Back 54

It develop benchmarks for embedded system and organise their benchmark to suit various application domain like digital media, java

Front 55

What are the 3 advantage of polling

Back 55

Minimum hardware interface is used

Programmer has complete control of the cpu

Easy to test n debug

Front 56

3 Disadvantage of polling

Back 56

Cpu cannot perform other task until data transfer is complete

Inefficent use of computer resource

Program execution is held up while waiting for I/o device to be ready

Front 57

3 Advantage of interrupt triggered technique

Back 57

Efficient use of cpu resource

Cpu can perform other tasks while transferring data

Allow prioritisation and pre emption

Front 58

2 Disadvantage of interrupt trigger

Back 58

More hardware interface is needed

More complex and difficult to debug

Front 59

What is burst mode

Back 59

It is also noe as block transfer mode. It take control of the data bus and only return the control after it has finish the data transfer.

It allows fast data transfer but cpu maybe suspended for a long period of time

Suitable for HDD file transfer

Front 60

What is cycle stealing

Back 60

It will release the control of data bus transferring one word of data.

Cpu maybe be suspended but only for a short period of time. It has slower transfer rate compare to burst mode but has the better cpu respond. It requires more complex hardware

Front 61

What is transparent mode

Back 61

It only take control of the data bus when cpu is not using. It has zero impact on cpu responds but it has the slowest transfer rate among the 3 mode. More complex data is needed to check when the cpu is not using