SLR 1.1 Systems architecture

Question 1

What does ALU stand for?

Answer 1

Arithmetic Logic Unit

Question 2

What is the role of the ALU?

Answer 2

The Arithmetic Logic Unit (ALU) carries out arithmetic operations or logical comparisons. This allows a program to make decisions.

Question 3

What does CPU stand for?

Answer 3

Central Processing Unit

Question 4

What are registers?

Answer 4

“Tiny areas of extremely fast memory located in the CPU normally designed for a specific purpose, where data or control information is stored temporarily.”

Question 5

What does PC stand for (in the context of the CPU)?

Answer 5

Program Counter

Question 6

What is the role of the PC?

Answer 6

“It is a register in the control unit which holds the address of the next instruction to be executed.”

Question 7

What does ACC stand for?

Answer 7

Accumulator

Question 8

What is the role of the ACC?

Answer 8

“To hold the data currently being processed by the CPU. Any data to be processed is stored temporarily in the accumulator, the results ending up back in the accumulator before being stored in the memory.”

Question 9

What does MAR stand for?

Answer 9

Memory Address Register

Question 10

What is the role of the MAR?

Answer 10

“It is a register in the CPU that stores the address in memory of the next instruction to be fetched, decoded and executed.”

Question 11

What does MDR stand for?

Answer 11

Memory Data Register

Question 12

What is the role of the MDR?

Answer 12

“It is a register in the CPU that stores data being transferred to or from memory.”

Question 13

What is an FDE cycle?

Answer 13

A Fetch, Decode and Execute cycle

Question 14

What happens during an FDE cycle?

Answer 14

“The complete process of retrieving an instruction from memory (RAM), decoding it and carrying it out. Also known as the instruction cycle.”

Question 15

What does the CPU consist of?

Answer 15

“The CPU is the main part of the computer, consisting of the registers, ALU and control unit.”

Question 16

What is “clock speed”?

Answer 16

“The clock speed is the frequency at which the internal clock generates pulses. The higher the clock rate, the faster the computer may work. The “clock” is the electronic unit that synchronises related components by generating pulses at a constant rate.”

Question 17

What are cores?

Answer 17

“Cores are the units responsible for the fetch-decode-execute cycle.”

Question 18

What is the cache?

Answer 18

Cache is extremely fast access memory within the CPU. Sections of a program and its data are copied to the cache as it is quick to access.

Question 19

What is Von Neumann Architecture?

Answer 19

A traditional computer architecture that forms the basis of most digital computer systems. A single control unit manages program control flow following a linear sequence of ‘fetch-decode-execute’ cycles.

Question 20

What is a ‘little man computer’

Answer 20

The Little Man Computer (LMC for short) is generally used to teach students, because it models a simple von Neumann architecture computer - which has all of the basic features of a modern computer.

Question 21

What is an embedded system?

Answer 21

An embedded system is a computer systems with a dedicated function within a larger mechanical or electrical system. For example washing machines, traffic lights, toasters and DVD players all have embedded systems - as do many, many other things!

Question 22

Name the main parts of a CPU

Answer 22

1. Arithmetic Logic Unit (ALU)
2. Control Unit (CU)
3. Cache
4. Registers

Question 23

Name the main registers a CPU has access to

Answer 23

1. Program Counter (PC)
2. Memory Address Register (MAR)
3. Memory Data Register (MDR)
4. Accumulator (ACC)

Question 24

What does the ALU do?

Answer 24

Performs calculations and logic decisions

Question 25

What does the CU do?

Answer 25

Sends signals to control how data moves around the processor

Question 26

What does the cache do?

Answer 26

Provides fast access to frequently used instructions/data

Question 27

What does the PC do?

Answer 27

Holds the address in memory of the next instruction to be processed

Question 28

What does the MAR do?

Answer 28

Holds the address of where data is to be fetched from or stored to

Question 29

What does the MDR do?

Answer 29

Holds the data fetched from or to be written to memory

Question 30

What are the units for clock speed?

Answer 30

Hertz (cycles per second - this shows how many instructions can be fetched, decoded and executed each second). Modern computers can do billions of FDE cycles per second so are rated in Giga Hertz