Real-Time Computing: Difference between revisions
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* https://en.wikipedia.org/wiki/Real-time_computing | * https://en.wikipedia.org/wiki/Real-time_computing | ||
* Real-Time Computing: A New Discipline of Computer Science and Engineering https://kabru.eecs.umich.edu/papers/publications/1994/ramanathan-shin-ieee-proceedings.pdf | |||
=Internal= | =Internal= | ||
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Formally, a system is said of be real-time if the correctness of an operation depends not only upon its logical correctness, but also upon the time in which the operation is performed. Real-time systems are classified by the consequences of missing a deadline: | Formally, a system is said of be real-time if the correctness of an operation depends not only upon its logical correctness, but also upon the time in which the operation is performed. Real-time systems are classified by the consequences of missing a deadline: | ||
* <span id='Hard'></span>'''Hard''' Real- | * <span id='Hard'></span>'''Hard''' Real-time System - missing a [[#Deadline|deadline]] is a total system failure. | ||
* <span id='Firm'></span>'''Firm''' Real- | * <span id='Firm'></span>'''Firm''' Real-time System - infrequent [[#Deadline|deadline]] misses are tolerable, but may degrade the system's quality of service. The usefulness of a result is zero after its [[#Deadline|deadline]]. | ||
* <span id='Soft'></span>'''Soft''' Real-time System - the usefulness of a result degrades after its deadline, degrading the system's quality of service. | |||
=Real-time Operating System= | =Real-time Operating System= | ||
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An operating system intended to serve real-time applications that process data as it comes, without [[#Buffer_Delay|buffer delays]]. The system attempts to insure [[#Real-time_Constraint|the guaranteed response time]], possibly at the expense of the throughput. | An operating system intended to serve real-time applications that process data as it comes, without [[#Buffer_Delay|buffer delays]]. The system attempts to insure [[#Real-time_Constraint|the guaranteed response time]], possibly at the expense of the throughput. | ||
=Real-time Constraint= | =<span id='Deadline'></span>Real-time Constraint= | ||
A ''real-time constraint'' is a guaranteed response within a specified time constraint between event to system response. Real-time constraints are also referred to as "deadlines". Deadlines must always be met, regardless of system load. For [[#Hard|hard]] and [[#Firm|firm]] real-time systems, the usefulness of a result is zero after its deadline. | A ''real-time constraint'' is a guaranteed response within a specified time constraint between event to system response. Real-time constraints are also referred to as "deadlines". Deadlines must always be met, regardless of system load. For [[#Hard|hard]] and [[#Firm|firm]] real-time systems, the usefulness of a result is zero after its deadline. | ||
=Near real-time= | |||
=Buffer Delay= | =Buffer Delay= | ||
=Jitter= | =Jitter= | ||
Latest revision as of 00:52, 19 April 2018
External
- https://en.wikipedia.org/wiki/Real-time_computing
- Real-Time Computing: A New Discipline of Computer Science and Engineering https://kabru.eecs.umich.edu/papers/publications/1994/ramanathan-shin-ieee-proceedings.pdf
Internal
Overview
A real-time system is subject to a "real-time constraint" - a guaranteed response within a specified time constraint between event to system response. Real-time systems control an environment by receiving data, processing it, and returning the results sufficiently quickly to affect the environment at that time.
Formally, a system is said of be real-time if the correctness of an operation depends not only upon its logical correctness, but also upon the time in which the operation is performed. Real-time systems are classified by the consequences of missing a deadline:
- Hard Real-time System - missing a deadline is a total system failure.
- Firm Real-time System - infrequent deadline misses are tolerable, but may degrade the system's quality of service. The usefulness of a result is zero after its deadline.
- Soft Real-time System - the usefulness of a result degrades after its deadline, degrading the system's quality of service.
Real-time Operating System
An operating system intended to serve real-time applications that process data as it comes, without buffer delays. The system attempts to insure the guaranteed response time, possibly at the expense of the throughput.
Real-time Constraint
A real-time constraint is a guaranteed response within a specified time constraint between event to system response. Real-time constraints are also referred to as "deadlines". Deadlines must always be met, regardless of system load. For hard and firm real-time systems, the usefulness of a result is zero after its deadline.