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Myron Zimmerman on “What is real-time?”

Sep 14, 1997 — by Rick Lehrbaum — from the LinuxDevices Archive — 2 views

Here are Myron Zimmerman's answers:

  • What is real-time? — A real-time system provides specified system services with known timing and latency characteristics, so that applications can be designed and developed that meet perscribed timing constraints.

  • What is hard real-time? — In a hard real-time system, the timing constraints have an upper worst-case value, which if exceeded, cause the application to fundamentally fail.

  • What is soft real-time? — In a soft real-time system, the timing constraints do not have an upper worst-case value, but meet an acceptable statistical distribution of timings. In this case, occasional longer latencies either do not really cause failures, or the failure rates are acceptable.

  • Additional comments: — A related, but separate issue, is scheduling policies — be it deadline, fixed priority, etc. Each of these can either be hard or soft. It should be noted that quite a number of software and hardware issues impact real-time systems.

Panelist's bio: Myron Zimmerman is CTO and cofounder of VenturCom, a leading provider of software products and expertise for Windows-based, real-time, embedded, and control-oriented applications. Among early products, was a real-time implementation of the UNIX operating system. Zimmerman was VenturCom's first Director of Engineering and later served as the company's President, for eleven years. Zimmerman holds a Ph.D. in Atomic Physics from MIT.

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