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Lecture 1
Questions
- What are the three types of parallel processing?
- Multiple computers
- Multicore systems
- Multithreading
- What is the relation of time with respect to correctness in Realtime systems?
- Correctness is tied to whether the task is done with some deadline.
- This is not usually the case with other software systems.
- We would just call it a “slow” system as long as it produces the intended output
- What are the three types of time limits?
- Hard
- Firm
- Soft
- What is a hard time limit and examples?
- $t_{finish} > deadline \implies \text{incorrect}$
- Any safety critical industrial application’s event-triggered events
- A chemical plant’s pressure controller that has to trigger within 10s of an event else the plant may explode
- What is a firm time limit and examples?
- Completing a task beyond the deadline has no value but is not harmful either
- Rendering a frame after its successor has already been displayed
- What is a soft time limit and examples?
- Completing a task beyond the deadline has diminishing returns
- Stock trading
- What are the two reference points for defining timing constraints?
- Event-triggered
- Pre-scheduled
- What is latency?
- Event-triggering - completion
- What is jitter?
- Expected frequency - actual frequency
- Expected start time - actual start time
- What is the Harvard architecture?
- Separate buses for instruction and data