1.1 System Architecture

Question 1

Define CPU

Answer 1

The CPU is often thought of as the “brains” of the computer. The purpose of the CPU is to fetch, decode, and execute instructions.

Question 2

Define fetch-execute cycle

Answer 2

The CPU fetches the next instruction from RAM, it works out what to do with the instruction, then carries out the instruction.

Question 3

Define Control Unit

Answer 3

The control unit controls the flow of data inside the CPU (to registers) and outside the CPU to RAM and input/output devices.

Question 4

Define arithmetic logic unit

Answer 4

The ALU does all the calculations. It completes simple addition and subtraction, as well as comparisons e.g. < >=. It also performs logical operations, e.g. AND, OR.

Question 5

Define cache

Answer 5

The cache is very fast memory in the CPU. It is slower than the registers but faster than RAM. It stores frequently used data that the CPU can access quickly.

Question 6

Define Von Neumann

Answer 6

Von Neumann is based on the idea of a stored program concept. Both instructions and data are stored in the same memory in binary form.

Question 7

Define Memory Address Register (MAR)

Answer 7

The MAR holds the address of where data is to be fetched or stored.

Question 8

Define Memory Data Register (MDR)

Answer 8

The MDR holds the data fetched from or to be written to memory (RAM).

Question 9

Define program counter

Answer 9

The PC holds the address of the next instruction in memory.

Question 10

Define accumulator

Answer 10

The Accumulator holds the intermediate results of calculations.

Question 11

Define clock speed

Answer 11

This is the number of instructions a single processor core can carry out per second, e.g. desktop computers, equals 3.5 GHz (3 billion instructions per second).

Question 12

Define cache size

Answer 12

A larger CPU cache gives the CPU faster access to frequent used instructions without having to actually use instructions from RAM. This increases performance.

Question 13

Define number of cores

Answer 13

Each core in a CPU can process data independently. The more cores a CPU has the more instructions it can carry out at once.

Question 14

Define embedded systems

Answer 14

Embedded systems are computers, built-in to other devices like dishwashers and microwaves. They are dedicated systems so easier to design and produce.

Question 15

What is the processor?

Answer 15

It processes data, executes instructions, “brains of computer”, clock speed measure in cycles per second (Hertz)

Question 16

What is the typical speed of a processor?

Answer 16

MHz or GHz

Question 17

What is a core?

Answer 17

Executes instructions independently

Question 18

What is cache?

Answer 18

Fast and very small amount of memory on the processor chip. The cache acts as an intermediary between the processor and the main memory. As programs are executing, the cache holds commonly used instructions. A memory cache is a memory bank that is very fast and sits between the CPU and main memory. It is faster to access than RAM.

Question 19

What is clock speed?

Answer 19

There is an internal clock that happens on the pulse. If the clock speed increases, the faster the instructions are processed.

Question 20

What is a dual core processor?

Answer 20

It has two processors linked together within the same integrated circuit. It should have twice the processing power, but some software has not been written with dual core processors in mind.
A quad core processor has the sam problem but double the number of processors.

Question 21

What is the impact of increasing cache size?

Answer 21

Reduces the number of memory to disk transfers and so may speed up processing of these instructions.

Question 22

When might a dual core processor be no faster than a single core processor?

Answer 22

If the computer is running one program, it may not be any faster as instructions still have to be carried out in a certain sequence.

Question 23

What is Level 1 cache?

Answer 23

The data used frequently by the CPU so it is available almost instantaneously. RAM is farther away from the CPU so is much slower to receive an instruction or data from the cache.

Question 24

What is level 2 cache?

Answer 24

Affects the performance of the CPU greatly, as this is closest to RAM and reduces wait time. Whether the cache is on the CPU board will also affect performance.

Question 25

How do you calculate cycles per second?

Answer 25

Number of cores x clock speed

Question 26

What are registers?

Answer 26

Immediate memory, which is very fast temporary memory on the CPU to speed up access.

Question 27

What is the Control Unit?

Answer 27

Hardware is monitored
Input/ output of devices and response of instructions to the CPU
Data flow is controlled within the CPU
Sends control signals between internal components memory read/ memory write/ hard disk drive read/ input output write

Question 28

What are internal components?

Answer 28

RAM, ROM, processor, buses, I/o controllers

Question 29

What are external components?

Answer 29

Keyboard, mouse, printer, secondary storage

Question 30

What is a bus?

Answer 30

A set of parallel wires connecting two or more independent components of a computer system in order to pass signals between them. Data bags, address bus, control bus.

Question 31

What is the address bus?

Answer 31

Carries addresses from the processor to main memory
One directional
The processor generates an address
All instructions/ data are returned on the data bus

Question 32

What is the data bus?

Answer 32

Carries data/ instructions from main memory to processor (or from secondary storage devices)
Two way (bidirectional)
Data can be read/ written

Question 33

What is the control bus?

Answer 33

Control signals are sent along the control bus e.g memory read and memory write

Question 34

What are peripherals?

Answer 34

Any devices not directly connected to the CPU e.g mouse, CD-ROM, printer etc
I/O devices

Question 35

What is the fetch-decode-execute cycle?

Answer 35

Fetch next instruction and associated data from main memory
Interprets instruction
Perform the instruction

Question 36

What is von Neumann architecture?

Answer 36

Store the program instructions and the data all in memory

Question 37

MAR and MDR

Answer 37

The address of the instruction to be executed is copied from the PC to MAR. The instruction at that address is fetched from memory and copied to the MDR. MAR knows where to look for data, MDR keeps hold of the data until ready to be used by the CPU.

Question 38

How does the clock chip maintain a constant speed?

Answer 38

Using a vibrating crystal