Systems Architecture

Question 1

What are the main components of a computer?

Answer 1

CPU (central processing unit), main memory, secondary storage, input devices, output devices

Question 2

What is the purpose of a CPU?

Answer 2

The purpose of the CPU is to process data and execute programs

Question 3

What are the components of a CPU?

Answer 3

Control Unit, Arithmetic Logic Unit, RAM (main memory), Buses, Registers, Clock

Question 4

What is the ALU?

Answer 4

The Arithmetic Logic Unit (ALU) performs all the arithmetic operations and logical decisions

Question 5

What is the CU?

Answer 5

The Control Unit uses electrical signals to control the timing and the flow of data around the CPU. It is responsible for fetching and decoding instructions so that they can run on the processor.

Question 6

What is RAM?

Answer 6

Random Access Memory (primary storage) is the main memory of the computer where programs, data and operating systems are stored when the computer is in use.

Question 7

What are buses?

Answer 7

They are just sets of wires, used to transfer data and signals between the CPU and memory

Question 8

What are the different buses and what do they do?

Answer 8

Control bus - carries control signals to tell the memory or the processor what to do next
Address bus - carries memory addresses from processor to memory
Data bus - carries data and instructions both ways between memory and CPU

Question 9

What is Von Neumann Architecture?

Answer 9

Computer programs and data are stored in the SAME RAM memory

Question 10

What are registers?

Answer 10

Registers are extremely small, extremely fast memory located in the CPU that hold small amounts of data needed as part of the fetch-execute cycle. Each register has its own specific purpose.

Question 11

What is the purpose of the clock?

Answer 11

The clock keeps related components in sync by generating pulses at a constant rate.

Question 12

What are the different registers and what are their purposes?

Answer 12

Program Counter (PC) - holds the address of the next instruction to be executed
Current Instruction Register (CIR) - holds the current instruction
Memory Address Register (MAR) - Holds the addresses that are about to be sent down the address bus to memory
Memory Data Register (MDR) - Holds data or instructions that have travelled up the data bus from the memory
Accumulator (ACC) - Holds the result of the most recent calculation by the ALU.

Question 13

What is Cache?

Answer 13

Cache is memory that is similar to RAM, but is much faster and therefore more expensive. It is located very close to the CPU

Question 14

What are the 4 things that affect how well your processor works?

Answer 14

Cache memory
Clock Speed
Multiple cores
Speed of Memory

Question 15

How does clock speed affect how well the processor works?

Answer 15

Higher clock speed - faster performance but runs hotter and consumes more power (overclocking)
Lower clock speed - lower performance, less costly, needs less power so good for battery life in laptop
Clock speed is measured in Hertz.
The clock speed measures the number for fetch-decode-execute cycles that can take place in 1 second
A clock speed of 3.5GHz can perform up to 3.5 billion instructions per second.

Question 16

What is a dual core processor?

Answer 16

Two processors working independently at the same time
They will fetch, decode and execute programs simultaneously
Therefore they can process more instructions at one time - if that can be programmed

Question 17

Will multiple core processors run faster than a singular one?

Answer 17

Not necessarily, as software may be designed to only run on 1 core, some tasks cannot be split over multiple cores. Other things also affect speed of processor.

Question 18

What is an embedded system?

Answer 18

An embedded system is a computer system with a dedicated function, inside a larger mechanical unit.

Question 19

What is a non-embedded system?

Answer 19

A non-embedded system is a computer system with multiple functions, referred to a general purpose machine.

Question 20

What are the differences between an embedded and non-embedded system?

Answer 20

An embedded system is typically:
smaller in size
lower power
lower cost
lower processing power
lower memory

Question 21

What are the characteristics of an embedded system?

Answer 21

An embedded system is a single microprocessor that includes RAM, ROM and a CPU.
Embedded systems have limited functions, and can’t easily be changed.
And embedded system is frequently used to control a device using limited inputs and outputs.
They’re often invisible to the user.

Question 22

What are some examples of an embedded system?

Answer 22

Heating thermostats
Dishwashers
Washing machines
Coffee machines
Traffic lights
Hospital equipment

Question 23

What are the three operations in the Fetch-Execute cycle?

Answer 23

Fetch - causes the next instruction and any data involved to be fetched from main memory
Decode - decodes the instruction
Execute - carries out the instruction

Question 24

Describe the process of the Fetch operation in the Fetch-Execute cycle.

Answer 24

1. Firstly, address of next instruction copied from PC into MAR
   2a. The contents of the MAR are sent down the address bus. A READ signal is sent down the control bus. the main memory looks at what is in that memory location and sends it up the data bus to the MDR
   2b. At the same time, the PC is incremented(goes up by 1) - because it always holds the address of the NEXT instruction
2. The instruction in the MDR is copied to the CIR