Week 6 Flashcards
What is Parallel Computing?
Improve performance by performing multiple computations in parallel
What is Flynn’s Taxonomy?
Classification of computer architectures based on number of instruction and data streams they can handle simultaenously
What is an Instruction Stream?
Sequence of instructions; arithmetic, data transfer and branching
What is a Data Stream?
Consists of operands (constants, variables and memory addresses)
What is Single Instruction Single Data (SISD)?
Sequential computer with no data or instruction parallelism
Older single-core CPUs and simple microcontrollers
What is Multiple Instruction, Single Data (MISD)?
Multiple instructions operate on one piece of data simultaneously
Used for fault tolerance
Rare in practice
Eg. Space shuttle flight systems
What is Triple Modular Redundancy?
Majority vote of three independent systems or processors
Space satellite systems often use TMR
What is Single Instruction, Multiple Data (SIMD)?
Execute the same instruction on multiple data points simultaneously
What are SIMD computers good for?
Good for vector operations including image and audio processing
What are SIMD computers not good for?
SIMD computers are not suitable when the type of instruction depends on the data
What is a GPU (Graphics Processing Unit)?
GPU contains many ALUs to perform mathematical operations in parallel
GPU based on SIMD architecture
How to GPUs compare to CPUs?
GPUs have more ALUs and rely less on cache
GPUs have higher throughput and higher latency
What are Threads?
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
What is Multiple Instruction, Multiple Data (MIMD)?
Multiple processors simultaneously execute different instructions on different pieces of data
What are Multi Core Processors?
A multi-core processor puts many CPU cores on one chip
What are Multiprocessors?
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
What are Multicomputers?
Different computers connected together
What is the benefit of Shared Memory (Multiprocessors)?
Faster communication
What is the benefit of Distributed Memory (Multicomputers)?
Allows for higher bandwidth
What are the 2 energy problems the world faces?
- Energy produces greenhouse gas and emission
- Energy Poverty - low emissions of the poor as they lack access to modern energy or tech
What is the solution to the 2 energy problems?
- Reducing greenhouse gas emissions
- Removing gases from the atmosphere
What is the Energy Demand for ICT?
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
What is the Quick and the Dead?
Historically (like the Wild West), the processor world consisted of the quick (those with high SPEC marks) and the dead (those without)
What is the Energy-Efficient and the Dead?
Today, the processor world increasingly consists of the energy-efficient (those with high SPEC marks/watt) and the dead (those without)
What is the Sleep State?
Up until circa 1990 there were only 2 power states
On
Off
What are Intermediary states (like sleep mode)?
Low power consumption
Quick recovery to active state based on user input
What is the Advanced Configuration and Power Interface (ACPI)?
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
What are Global States G0-G3?
Apply to the entire system and are visible to the user
What are Device States D0-D3?
States of particular devices (eg. disks, keyboards) generally not visible to the user
What are Processor States C0-C3?
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
What are Performance States P0-P15?
Power consumption and capability states within the active states (substates of D0/C0)
Processor could save energy by scaling down power and clock frequency
What is Power Usage Effectiveness?
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
What are the values of the PUE chart?
PUE Level of efficiency
1.0 Ideal
1.2 Very efficient
2 Average
2.5 Inefficient
3 Very Inefficent
What is the Open Compute Project (OCP)?
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
What are 3 ways to Lower Power Usage Effectiveness
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
