1.1.1 Hardware: Architecture

Question 1

What is the ALU and what does it do?

Answer 1

The Arithmetic-Logic Unit (ALU) carries out mathematical calculations and logic operations.

Question 2

What is the CIR and what does it do?

Answer 2

The Current Instruction Register (CIR) contains the current instruction during processing.

Question 3

What is the MDR and what does it do?

Answer 3

The Memory Data Register (MDR)

Question 4

What is the MAR and what does it do?

Answer 4

The Memory Address Register (MAR)

Question 5

What is the CU and what does it do?

Answer 5

The Control Unit (CU)

Question 6

What does the Accumulator do?

Answer 6

The Accumulator

Question 7

What is the PC and what does it do? (Not referring to the term ‘Personal Computer’)

Answer 7

The Program Counter (PC)

Question 8

Where is the CIR located within the CPU?

Answer 8

The Control Unit.

Question 9

Where is the MDR located within the CPU?

Answer 9

The Arithmetic Logic Unit.

Question 10

Where is the MAR located within the CPU?

Answer 10

The Control Unit.

Question 11

Where is the Program Counter located within the CPU?

Answer 11

The Control Unit.

Question 12

Where is the Accumulator located within the CPU?

Answer 12

The Arithmetic Logic Unit.

Question 13

What happens in the ‘fetch’ portion of the FDE cycle?

Answer 13

1) Address of the next instruction is transferred from the PC to the MAR, and the PC increments by 1. The address bus carries the address of the location of the data in memory.
2) The instruction stored in memory is carried by the data bus to the MDR.
3) The instruction in the MDR is carried by the data bus to the CIR.

Question 14

What happens in the ‘decode’ portion of the FDE cycle?

Answer 14

1) The instructions are decoded in the CIR.
2) If additional data is required, the request is passed to the MAR, and then travels along the address bus to the main memory, where data is fetched.
3) The MDR fetches the data/instruction from memory.

Question 15

What happens in the ‘execute’ portion of the FDE cycle?

Answer 15

1) The data/instruction is passed to the Accumulator.
2) The instruction is executed, and the result is held in accumulator or sent to main memory.

Question 16

What happens in the FDE Cycle?

Answer 16

1) Address of the next instruction is transferred from the PC to the MAR, and the PC increments by 1. The address bus carries the address of the location of the data in memory.
2) The instruction stored in memory is carried by the data bus to the MDR.
3) The instruction in the MDR is carried by the data bus to the CIR.
4) The instructions are decoded in the CIR.
5) If additional data is required, the request is passed to the MAR, and then travels along the address bus to the main memory, where data is fetched.
6) The MDR fetches the data/instruction from memory.
7) The data/instruction is passed to the Accumulator.
8) The instruction is executed, and the result is held in accumulator or sent to main memory.

Question 17

What is the difference between RAM and ROM?

Answer 17

Random Access Memory (RAM) is very fast, Volatile (Think liable to change), holds temporary data only and capable of reading and writing.

Read-Only Memory (ROM) is relatively slow, Non-volatile, holds permanent data only and can only be read from, not written to (Use the component name to help remember this).

Question 18

Recite the units of storage including capacity.

Answer 18

Byte (B) = 8 Bits
Kilobyte (KB) = 1024 Bytes
Megabyte (MB) = 1024 Kilobytes
Gigabyte (GB) = 1024 Megabytes
Terabyte (TB) = 1024 Gigabytes
Petabyte (PB) = 1024 Terabytes
Exabyte (EB) = 1024 Petabytes
Zettabyte (ZB) = 1024 Petabytes
Yottabyte (YB) = 1024 Zettabytes

Question 19

What is the function of the Address Bus?

Answer 19

The Address Bus carries addresses of the memory location being written to or read from.

Question 20

What is the function of the Data Bus?

Answer 20

The Data Bus carries data between the processor and memory and also other components.

Question 21

What is the function of the Control Bus?

Answer 21

The Control Bus carries control signals from the control unit to communicate with other components and devices.

Question 22

How does clock speed affect the performance of the CPU?

Answer 22

The faster the clock speed, the faster the instructions are processed, the more applications (in the FDE cycle) occur per second.

A faster clock speed increased performance, but draws more power and emits more heat.

Question 23

What is Cache Memory and what does it do?

Answer 23

Cache is a small amount of very fast, expensive memory in the CPU.

Cache allows temporarily stored data to be accessed faster than regular main memory (RAM).

Question 24

How does Cache Memory affect the performance of the CPU?

Answer 24

Cache memory inproves the performance of the CPU as it is able to provide instructions and data to the CPU at a much faster rate than other system memory such as RAM.

Question 25

What are the 3 levels of Cache Memory?

Answer 25

Level 1 Cache is very expensive, fast and low capacity. Level 1 Cache is located inside the CPU.

Level 2 Cache is fairly expensive, relatively fast and medium capacity. Level 2 Cache is located close to the CPU.

Level 3 Cache is less expensive than Level 2 Cache but more so than Main memory, slower than Level 2 Cache but faster than Main memory and large relative capacity. Level 3 Cache is located outside the CPU.

Question 26

How does the number of cores affect the performance of the CPU?

Answer 26

More cores mean the processor can perform multiple operations at once. The more cores available the more operations the processor can perform in one cycle. Factors such as one operation requiring the result of another operation means this doesn’t double or quadruple performance, but can make the CPU much faster nevertheless.

Question 27

What are the benefits of Cache Memory?

Answer 27

The data used most often by the CPU is held in Level 1 Cache so is instantly available.

In most systems, other data neede by the CPU is accessed from the Level 2 Cache 95% of the time.

More cache memory improves system performance.

Question 28

What is an Input Device and what does it do?

Answer 28

Allows interaction with a computing system, allowing data to be entered.

Question 29

What is an Output Device and what does it do?

Answer 29

Allows data to be received from a computing system.

Question 30

What is Main Memory?

Answer 30

Holds data, instructions and programs durrently in use.