System architecture, memory and storage

Question 1

What is the purpose of the CPU?

Answer 1

To execute instructions stored in the memory, through the FDE cycle.

Question 2

Explain each stage of the FDE cycle

Answer 2

Fetch, The instruction is fetched from memory
Decode, The instruction is interpreted
Execute, The instruction is carried out

Question 3

What is the function of the ALU?

Answer 3

The Arithmetic Logic Unit carries out mathematical and logical operations such as AND, OR and Binary shifts.

Question 4

What is the function of the CU?

Answer 4

The Control Unit co-ordinates the FDE cycle by controlling the sequence of instructions,regulating processor timing etc.

Question 5

List the special-purpose registers found in the CPU

Answer 5

MAR - Memory Address Register
MDR - Memory Data Register
PC - Program Counter
Accumulator

Question 6

What is the funtion of the MAR?

Answer 6

Holds the location in memory of the current instruction or data to be fetched or stored.

Question 7

What is the function of the MDR?

Answer 7

Temporarily holds data when fetched from or to be sent to memory.

Question 8

What is the function of the PC?

Answer 8

Holds the memory addess of the next instruction to be processed.

Question 9

What is the function of the accumulator?

Answer 9

Stores the results of operations carried out in the ALU.

Question 10

State the three main factors affecting CPU performance

Answer 10

Clock Speed
Cache Size
Number of Cores

Question 11

Describe how Clock Speed affects CPU preformance

Answer 11

Everything the processor does occurs on a tick therefore a faster clock means more instructions FDE’d
Measured in GHz (n billion of cycles per second)

Question 12

Describe how Cache Memory affects CPU performance

Answer 12

As Cache stores frequently used memory and can be accessed faster than RAM, the more data stored in the Cache the more efficient the CPU

Question 13

Order the following by ascending access speed:
Physical RAM, CPU registers , Disc Storage, Cache

Answer 13

CPU registers
Cache
Physical RAM
Disc Storage

Question 14

Order the following by ascending cost per byte:
Physical RAM, CPU registers , Disc Storage, Cache

Answer 14

CPU registers
Cache
Physical RAM
Disc Storage

Question 15

Order the following by ascending capacity:
Physical RAM, CPU registers , Disc Storage, Cache

Answer 15

Disc Storage
Physical RAM
Cache
CPU registers

Question 16

Describe how number of cores affects CPU performance

Answer 16

Each core can process 1 operation per clock cycle therefore a dual core for example could theoretically perform 2 simultaneously.

Question 17

Explain why a dual core processor or 2x clock speed may not translate to 2x CPU performance

Answer 17

• Software must support multiple cores
• The result of an operation may be required for the next
• Bottlenecks such as Cache size

Question 18

What is an embedded system and it’s characteristics?

Answer 18

A reliable, minimal resource computer built into a piece of equipment to perform a specific function.
They cannot be modified once manufactured as they are controlled by ROM

Question 19

Outline the differences between RAM and ROM

Answer 19

RAM - Volatile (all data lost when computer turned off), Used for working instructions and data, can be read from and written to

ROM - Non-volatile, used for start-up instructions and embedded systems, can only be read from

Question 20

State what is meant by virtual memory

Answer 20

Virtual memory is a form of non-volatile memory, typically a part of the HDD or SSD dedicated to behave like RAM. When the program stored in the hard disk is needed it is swapped out with something else in the RAM

Question 21

Ouline 3 examples of solid state storage devices

Answer 21

Internal Solid State
USB Memory stick
Memory Card