Embedded Systems & Firmware

What is the difference between hard real-time and soft real-time?

  1. AHard real-time is built only in hardware, soft only in software
  2. BHard real-time is slow and soft real-time is fast
  3. CIn hard real-time, missing a deadline even once is a system failure; in soft real-time, occasional lateness only degrades quality
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Answer: C. In hard real-time, missing a deadline even once is a system failure; in soft real-time, occasional lateness only degrades quality

Hard real-time examples include automotive airbag, engine and brake control, where missing a deadline can cause a serious accident. Meeting deadlines even in the worst case must be verified at design time. Soft real-time examples include video and audio playback, where occasional lateness only causes minor glitches. Which category applies greatly changes how rigorous the verification must be.

  • A. It is not about how the system is built.
  • B. It is about how strictly deadlines must be met, not speed.
  • C. Correct. Airbag and brake control are hard real-time examples.
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