1.2 Latency vs Throughput Flashcards
Generally, you should aim for maximal throughput with acceptable latency
What is latency?
Latency is the time to perform some action or to produce some result.
Latency is the time it takes for data to travel from one point to another in a network. It is often measured in milliseconds.
Throughput is the number of such actions or results per unit of time.
What is throughput?
Throughput is the amount of data that can be processed or transmitted in a given amount of time. It is usually measured in bits per second (bps) or bytes per second.
True or False: Latency and throughput are the same thing.
False. Latency measures delay, while throughput measures the amount of data transferred.
Fill in the blank: High latency can lead to _______ in data transmission.
delays
Which of the following factors can affect latency? (A) Network congestion (B) Cable length (C) Routing devices (D) All of the above
D) All of the above
What is a common unit of measurement for throughput?
Throughput is commonly measured in bits per second (bps) or bytes per second.
Short answer: Why is low latency important for online gaming?
Low latency is important for online gaming because it reduces delays, allowing for real-time interactions between players.
True or False: Increasing throughput always reduces latency.
False. Increasing throughput does not guarantee lower latency.
What does a high throughput indicate about a network?
A high throughput indicates that a network can handle a large amount of data transfer effectively.
Multiple choice: Which scenario may have high latency? (A) A local network (B) Satellite internet (C) Fiber optic connection
B) Satellite internet
How has High Level Synthesis design methodology impacted the relationship between Systems designers and Hardware designers?
The High Level Synthesis design methodology has fundamentally changed the traditional boundaries between Systems designers and Hardware designers in several ways:
Both groups now use the same input language (C++ / System C) to specify their models, eliminating the previous language barrier
They are exposed to the same terminology and concepts, creating a shared technical vocabulary
Hardware designers are now encountering systems terms they previously had little exposure to
The traditional barrier between these two roles has been substantially reduced or eliminated entirely
This convergence has created a need for hardware designers to understand systems concepts more thoroughly
The unified approach has led to better integration between systems and hardware design processes
What is latency and how is it measured in hardware design?
Latency is a fundamental concept in hardware design that refers to the time required to perform an action or produce a result:
It is measured strictly in units of time
Common units include:
Hours
Minutes
Seconds
Nanoseconds
Clock periods
It represents the duration from start to completion of a single operation
In hardware design, it’s often converted to clock periods for practical implementation
It’s a critical metric for determining system responsiveness
Understanding latency is essential for meeting timing requirements in hardware designs
What is throughput and how is it measured in hardware design?
Throughput represents the rate at which actions are executed or results are produced:
It is measured in units of production per unit of time
Examples of units include:
Cars per day
Memory words per second
I/O samples per second
Iterations per minute
Bits per second
In memory systems, it’s often referred to as “memory bandwidth”
It represents the system’s processing capacity over time
Can be expressed in various ways depending on the application
In hardware design, it’s often converted to units per clock period
Understanding throughput is crucial for meeting performance requirements
How are latency and throughput illustrated in the manufacturing example provided?
The manufacturing example demonstrates these concepts through a car assembly line:
Latency:
Takes 8 hours to manufacture one complete car
Represents the time from start to finish for a single unit
Measured from when assembly begins to when car is complete
Throughput:
Factory produces 120 cars per day
Can be expressed as 5 cars per hour
Represents the rate of production
Shows how many units can be completed in a given time period
Demonstrates that multiple units can be in different stages of production simultaneously
This example shows how latency and throughput are different but related concepts in a practical setting.
How does one translate design requirements into practical latency and throughput measurements for hardware design?
The translation process involves several steps and calculations, as shown in the communications device example:
Given Requirements:
Clock frequency: 100MHz
Available computation time: 1000ns
Throughput: 640 Mbits/second
Word width: 64 bits
Latency Calculation:
Convert 1000ns to clock periods
Formula: 1000ns × (1s/10^9ns) × (100×10^6 clock periods/1s)
Result: 100 clock periods
Throughput Calculation:
Convert 640 Mbits/s to words per clock period
Formula: (640×10^6 bits/s) × (1 word/64 bits) × (1s/100×10^6 clock periods)
Result: 0.1 words/clock period
Can be expressed as “one word every 10 clock periods”
What is the common misconception about expressing throughput in tools, and what’s the correct way?
The final clarification in the text reveals important distinctions about throughput expression:
Incorrect but Common Usage:
Some tools express throughput simply in clock periods
In the example, they would report throughput as 10
This is technically incorrect but used for convenience
Omits the proper units that should be included
Correct Usage:
Should be expressed in units per unit of time
Complete units should be specified
In the example, should be expressed as words per clock period
Or alternatively, clock periods per word with clear specification
Proper units provide clearer understanding of the actual throughput
Helps avoid confusion and misinterpretation of specifications
