Hardware - CPU Performance

Question 1

what is the function of the clock speed

Answer 1

determines number of fetch-execute-decode cycles per second
- every action in CPU happens within a tick of the clock / clock cycle

Question 2

what is clock speed measure in

Answer 2

Hertz (Hz)

Question 3

how many cycles would a 3.8 GHz processor have

Answer 3

3.7 billions times per second

Question 4

what is Cache size

Answer 4

temporary storage of copies of data + instructions being ** read to + written from** the main memory

Question 5

what are the advantages of the speed of cache memory

Answer 5

• operates must faster than main memory –> data transferred in and out of cache memory quicker
• much quicker to access than RAM –> makes CPU more efficient –> since less time waiting for data to be transferred

Question 6

why are copies of data and instructions stored in Cache

Answer 6

• want to avoid retrieving data / instructions from the main memory as much as possible –> takes more time
• save time by have cache memory* already in the processor

Question 7

what is the system cache uses to optimise speed

Answer 7

• there are 2 or 3 levels of cache
• *fastest cache** = smallest capacity = Level 1 cache
• CPU will optimise use of fastest cache before using next level , or RAM , to improve performance speed

Question 8

describe the difference type of levels within cache

Answer 8

L1:
- fastest , but smallest in size
- hold most frequently use instructions / data
L2:
- bigger capacity, but slower in speed
- holds less frequently used instructions + data

Question 9

what is a core

Answer 9

a processor (complete copy of CPU)

Question 10

what is the function of different numbers of cores

Answer 10

• 1 core can process one operation per clock cycle
• dual-core = 2 operations simultaneously
• quad-core = 4 operations simultaneously

Question 11

does doubling the number of cores simply double the overall speed?

Answer 11

No
- core communicate with each other –> takes time + efficiency
- many programs are not designed for multiple core –> will not work

Question 12

what are the factors that will affect the speed of the CPU

Answer 12

• cache size
• clock speed
• number of cores

Question 13

what is an instruction set

Answer 13

a processors list ofall its specific commands, written in machine code that can be processed + executed by a CPU

Question 14

what is each command associated with

Answer 14

machine code

Question 15

what is a mnemonic

Answer 15

mnemonics represent assembly language instructions / machine code to make it easier for humans to understand

Question 16

what is a embedded system

Answer 16

• a smaller computer system with a dedicated function within a larger system, device or machine.

Question 17

what is the purpose of embedded systems

Answer 17

control the device and to allow a user to interact with it.

Question 18

do embedded systems need a full operating system and why?

Answer 18

NO
- only perform limited + very specific tasks
- their input is frequently controlled by a button press / switch

Question 19

give 5 examples of ab embedded system

Answer 19

• domestic appliances - dishwashes, TV
• cars
• security systems
  -central heating system
• vending machines

Question 20

advantages of embedded systems compared to general-purpose computers include:

Answer 20

• limited number of functions = they are cheaper to design and build.
• smaller
• require less power –>some devices run from batteries
• low cost per unit –> can be built using cheaper, less powerful processors
  .

Question 21

what are the limitations of embedded systems

Answer 21

• limited processing resources = more difficult to program + interact with

Question 22

why must embedded systems be reliable

Answer 22

cannot be modified once manufactured –> the program that controls it is held in the Read Only Memory (ROM)