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Comment by karmakaze | Hacker News Reader

That depends on whether we're talking about hard-realtime or soft-realtime.

[0] https://www.google.com/search?q=hard-realtime+soft-realtime

> A hard-real time system is a system in which a failure to meet even a single deadline may lead to complete or appalling system failure. A soft real-time system is a system in which one or more failures to meet the deadline are not considered complete system failure, but that performance is considered to be degraded.

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even in the case of soft-realtime we don't say the system is real-time because it's fast. We say its realtime because majority of the time it meet its deadline.

Yes, at the same time I don't know if I'd characterize a soft-realtime system as slow. One way to meet deadlines is by being very efficient/fast, while keeping variance low (e.g. no stop the world gc).

By that definition, a phone call that always takes 10 seconds for one side to hear the other is realtime.

That would indeed be a realtime system by common definitions as long as that latency is guaranteed. Audio and video are commonly considered soft-realtime domains for exactly that reason.

Yep. If you mean low-latency, say that. Real-time is an unfortunate name, but it means what it means.

And phone … callthatju arousmpnnd is n’t realtime.

Technically not relevant but I know that a lot of early handhelds that repurposed RTOS for GUI felt slow, jumpy and unresponsive, perhaps because everything was polled? In that sense RTOS can be slow.

I think it felt that way because of bad design + slow hardware. You see the exact same thing by installing a modern windows version or some desktop like GNOME to low-end computers.

Who's that "we" ? For anyone I've worked with, real-time also implied "reaction time is faster than human perception"

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