Ian Bicking: the old part of his blog

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exokernel != microkernel.

The thing is, many new operating system designs *are* revolutionary, but that does not make them commercial successes in the desktop market (witness NeXT, BeOS, etc.)

Revolutionary new operating systems have a greater chance of succeeding when they are developed for a new and relatively closed platform, like game consoles, mobile phones or other embedded systems.
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by Michael Day