Fundamentals of Computer Architecture

Question 1

What are the 3 components of Von Neumann Architecture?

Answer 1

CPU, Main Memory, I/O devices

Question 2

What is a system bus?

Answer 2

• Allows the CPU to connect to other parts of the computer system using wires
• Facilitates communication between different components
• Some of the wires in a system bus are for sending signals, some for addresses and some for data

Question 3

What is a bus master

Answer 3

The part of the system bus responsible for coordinating the sending/receiving of data and signals and managing the processes

Question 4

What is a clock?

Answer 4

A repeated signal/pulse that flips between 1 and zero. Voltage, on and off. It is a point of reference for all components in the system so they can keep time with each other.

Question 5

What are logic gates and truth tables?

Answer 5

Logic gates are transistors in a system that act like switches. They can be set to on/off by either allowing or blocking an electrical signal. In essence they convert binary inputs to binary outputs with particular meanings i.e. these on/off positions can be combined to make logical ‘truths’ e.g. both ON = AND both OFF = NOT one ON and one OFF = OR - truth tables represent these combinations of input/output meanings in diagrammatic form

Question 6

Clock Cycle

Answer 6

Has a rising edge (voltage from 0-1) and falling edge (from 1-0)

Question 7

clock period

Answer 7

time to complete one clock cycle (t = 1/frequency)

Question 8

frequency

Answer 8

Frequency = 1/t ( t is clock period)

Question 9

If t (clock period) = 0.01 seconds (10 milliseconds) - what is the frequency for a clock cycle

Answer 9

1/0.01 = 100 hz

Question 10

What is a bit?

Answer 10

Smallest binary digit (a 1 or a 0)

Question 10

dynamic power

Answer 10

energy used by transistors to turn on / off

Question 10

what is a byte

Answer 10

Combination of 8 bits (sequence of 1s and 0s)

Question 11

CPU

Answer 11

circuit made up of transistors - can compute small amounts of information

Question 12

static power

Answer 12

energy used by transistors when dormant

Question 13

What are some of the challenges in the development of computer chips and increasing computing power

Answer 13

One of the main ways that computing power has increased has been decreasing the size of transistors and packing more onto a chip.

As the density of chips increases so does the heat generated.

Heat sinks and cooling fans can be used to remedy this but only so far.

Also transistors can only be made so small before the size starts to interfere with the flow of electricity on an atomic level making them unreliable

Question 14

What is an instruction?

Answer 14

• performs computation on small bits of data held in registers in the CPU
• examples of computation are:
  
  • evaluating to TRUE or FALSE (and can do things based on the outcome) , arithmetic like adding or subtracting, reading information from or loading/storing information into memory
• can be grouped with other instructions to make a program

Question 15

What does fetch/execute mean

Answer 15

CPU fetching instruction from memory and executing the instruction

Question 16

What is performance in relation to a CPU and what are the aspects we take into account when evaluating performance?

Answer 16

A cost benefit analysis on a system - i.e. how well it performs the task we want it to perform

• mips (million instructions per second)
• amount of power taken (e.g. in watts)
• cost of electricity
• ?dimensions

Question 17

What is power density and how is this calculated?

Answer 17

how much power is generated for the size of the chip - can give us an idea of heat generation

• power (Watts)/volume of the chip (cubic mm)
  e.g.
  chip size: 20 x 20 x 5 mm
  power: 40 Watts

power density = 40 / 2000mm^3 = 0.02W/ mm^3 or 20mW/mm^3

Question 18

Ways to improve performance

Answer 18

Pipelining - one instruction doesn’t need to finish before another is lined up

Multiscalar - Starting a new (unrelated) instruction before the current one has finished

Multicore processors - multiple processors/cpus

Branch prediction - based on previous patterns, predicting what instructions will execute next and lining them up (there is a cost if wrong)

Speculation - as above but carrying out the instuction (must be roll-back-able )

Question 19

What components make up the internal structure of a CPU

Answer 19

Address Register
Instruction Register
ALU (Arithmetic Logic Unit)
Control Unit

Question 20

What’s a general purpose computer

Answer 20

• a computer for a user who needs it to be able to do a wide variety
• has a large amount of memory on disk
• can run a variety of applications
• can run a range of operating systems and software
• can connect a variety of peripheral devices
• built from easily sourced components

Question 21

What’s a mobile processor

Answer 21

• chip optimised for the kind of processing needed on a small handheld device /performs multiple functions - rather than being separated into multiple chips / also optimised for running on limited power

Question 22

What’s an embedded systems

Answer 22

• preprogrammed, within a device e.g. a microwave - with set operations that they perform without a user needing to program - small small memory, often adheres to von neumann architecture

Question 23

What is Amdahl’s law

Answer 23

1/(1-P) + (P/n)

P=proportion of the system optimised, n= speedup factor