Everything removed from the sylabus (for 2022 only)

Question 1

What is a CPU

Answer 1

Central Processing Unit, controls the manipulation of data.

Question 2

What is the ALU?

Answer 2

Arithmetic / Logic Unit, performs arithmetic operations like addition and the logic operations like true and false

Question 3

What is the CU?

Answer 3

Control Unit, the circuits which coordinate the activities of the CPU

Question 4

What is a register

Answer 4

Quick, small stores of data within the CPU which exist as a temporary storage on the CPU

Question 5

What is Von Neumann Architecture?

Answer 5

• Instructions to be executed are stored along side the data in the memory. The stored programme concept
• Instructions are executed sequentially, one instruction at a time is fetched from the memory and passed to the CPU. Data and instructions cannot be accessed at the same time
• If the connection in the wire is too slow you got a Von Neumann bottle neck.

Question 6

Why do computers have a system clock?

Answer 6

It provides timing signals, producing a steady pulse of voltage to synchronise circuits. Eg: you only transfer data on the rising edge, or write data on the falling edge.

Question 7

How does the CPU use the system clock?

Answer 7

• The CPU is much faster that the other components, takes the system clock and raises its speed, this is the clock speed (Hz).
• The CPU needs a certain amount of clock ticks to execute an instruction

Question 8

What is the fetch execute cycle?

Answer 8

• Fetch: the next instruction is retrieved by the CPU from the main memory
• Decode: The instruction is broken down into its individual components (operator and operand)
• Execute: The CU activates the necessary circuits and the output of the stage is stored in the register, data may be written or read to main memory.

Question 9

What factors effect CPU performance?

Answer 9

• Clock speed
• Cache
• Cores

Question 10

How does clock speed effect CPU performance?

Answer 10

CPU carries out a set number of instructions per clock cycle. The higher the clock speed, the more instructions executed per second. Not designed to work at really high speeds, can overheat

Question 11

How does Cache effect CPU performance?

Answer 11

Cache exists to speed up the fetch stage, as cache is checked first. The larger the cache, the more instructions accessed faster, more likely to get a cache hit.

Question 12

How does Cache type effect CPU performance?

Answer 12

• trade off between cache speed and cache size.
• there are multiple levels of cache. L1 embedded in the chip (smallest and fastest, most used data)
• L2/L3 are larger and slower cache which is between the CPU and RAM.

Question 13

How does number of cores effect CPU performance?

Answer 13

A CPU can have multiple cores. When the software is optimised, multiple cores can allow multiple instructions to be executed simultaneously. Each core will have their own L1 Cache. Performance will increase for multiple instructions.

Question 14

What is an embedded system?

Answer 14

• A special purpose computer encapsulated by a larger system. Eg: microwave, hot tub, radio
• Only perform very specific tasks and cannot be easily reprogrammed

Question 15

Describe some characteristics of embedded systems.

Answer 15

Tend to:

• Have memory and CPU on the same chip
• Have more ROM than RAM (or no RAM at all)
• Work in real time (deals with the input straight away)

Question 16

benefits of embedded systems

Answer 16

• usually smaller than non embedded systems
• more reliable, work for longer and need less maintenance
• optimised for a particular task, so will work better
• likely to use ROM for their main memory, which is cheaper than RAM (which non embedded systems are likely to use)