Week 6

Question 1

What is Parallel Computing?

Answer 1

Improve performance by performing multiple computations in parallel

Question 2

What is Flynn’s Taxonomy?

Answer 2

Classification of computer architectures based on number of instruction and data streams they can handle simultaenously

Question 3

What is an Instruction Stream?

Answer 3

Sequence of instructions; arithmetic, data transfer and branching

Question 4

What is a Data Stream?

Answer 4

Consists of operands (constants, variables and memory addresses)

Question 5

What is Single Instruction Single Data (SISD)?

Answer 5

Sequential computer with no data or instruction parallelism

Older single-core CPUs and simple microcontrollers

Question 6

What is Multiple Instruction, Single Data (MISD)?

Answer 6

Multiple instructions operate on one piece of data simultaneously

Used for fault tolerance

Rare in practice

Eg. Space shuttle flight systems

Question 7

What is Triple Modular Redundancy?

Answer 7

Majority vote of three independent systems or processors

Space satellite systems often use TMR

Question 8

What is Single Instruction, Multiple Data (SIMD)?

Answer 8

Execute the same instruction on multiple data points simultaneously

Question 9

What are SIMD computers good for?

Answer 9

Good for vector operations including image and audio processing

Question 10

What are SIMD computers not good for?

Answer 10

SIMD computers are not suitable when the type of instruction depends on the data

Question 11

What is a GPU (Graphics Processing Unit)?

Answer 11

GPU contains many ALUs to perform mathematical operations in parallel

GPU based on SIMD architecture

Question 12

How to GPUs compare to CPUs?

Answer 12

GPUs have more ALUs and rely less on cache

GPUs have higher throughput and higher latency

Question 13

What are Threads?

Answer 13

GPUs hide latency by utilising threads

Process may be subdivided into multiple threads

Threads within a process share data, heap, and code, but have their own registers and stack

Question 14

What is Multiple Instruction, Multiple Data (MIMD)?

Answer 14

Multiple processors simultaneously execute different instructions on different pieces of data

Question 15

What are Multi Core Processors?

Answer 15

A multi-core processor puts many CPU cores on one chip

Question 16

What are Multiprocessors?

Answer 16

Two or more CPUs within a single computer system

CPUs communicate through shared memory variables

To modify shared variable, CPU locks variable so that no other processor can modify it

Question 17

What are Multicomputers?

Answer 17

Different computers connected together

Question 18

What is the benefit of Shared Memory (Multiprocessors)?

Answer 18

Faster communication

Question 19

What is the benefit of Distributed Memory (Multicomputers)?

Answer 19

Allows for higher bandwidth

Question 20

What are the 2 energy problems the world faces?

Answer 20

1. Energy produces greenhouse gas and emission
2. Energy Poverty - low emissions of the poor as they lack access to modern energy or tech

Question 21

What is the solution to the 2 energy problems?

Answer 21

1. Reducing greenhouse gas emissions
2. Removing gases from the atmosphere

Question 22

What is the Energy Demand for ICT?

Answer 22

ICT energy demand might rise to 8% of total electricity demand by 20230, in the best case, or 21% in the worst case

ICT sector used an estimated 4-6% of all electricity generated globally in 2020

Question 23

What is the Quick and the Dead?

Answer 23

Historically (like the Wild West), the processor world consisted of the quick (those with high SPEC marks) and the dead (those without)

Question 24

What is the Energy-Efficient and the Dead?

Answer 24

Today, the processor world increasingly consists of the energy-efficient (those with high SPEC marks/watt) and the dead (those without)

Question 25

What is the Sleep State?

Answer 25

Up until circa 1990 there were only 2 power states

On

Off

Question 26

What are Intermediary states (like sleep mode)?

Answer 26

Low power consumption

Quick recovery to active state based on user input

Question 27

What is the Advanced Configuration and Power Interface (ACPI)?

Answer 27

A standard device config and power management by the OS

Allows OS to control the amount of power supplied to various devices using different power states

Question 28

What are Global States G0-G3?

Answer 28

Apply to the entire system and are visible to the user

Question 29

What are Device States D0-D3?

Answer 29

States of particular devices (eg. disks, keyboards) generally not visible to the user

Question 30

What are Processor States C0-C3?

Answer 30

Processor power consumption and thermal management states - substates of G0

Processor states applied to individual cores

Synergy effects when multiple cores within same processor are shut down

Smartphones have both high-performance cores and energy saving cores

Question 31

What are Performance States P0-P15?

Answer 31

Power consumption and capability states within the active states (substates of D0/C0)

Processor could save energy by scaling down power and clock frequency

Question 32

What is Power Usage Effectiveness?

Answer 32

PUE is a metric used to determine energy efficiency of a data centre

PUE = Total facility energy/ IT energy = 1 + Non IT facility energy/ IT equipment energy

Lower the PUE more efficient

Question 33

What are the values of the PUE chart?

Answer 33

PUE Level of efficiency

1.0 Ideal

1.2 Very efficient

2 Average

2.5 Inefficient

3 Very Inefficent

Question 34

What is the Open Compute Project (OCP)?

Answer 34

OCP is a collaborative community focused on redesigning hardware to efficiently support the growing demands on compute infrastructure

Best practices for improving energy efficiency, cost and scalability

Question 35

What are 3 ways to Lower Power Usage Effectiveness

Answer 35

Bespoke Hardware :

Decide what to include and remove (Do you need GPUs, lights)?

Smarter Cooling:

Use locations with a cold climate

Mobile Computing:

Let mobile devices do a share of the work