See:
	* MicroChoices http://choices.cs.uiuc.edu/choices/uChoices.html
	* http://choices.cs.uiuc.edu/uChoices/Papers/uChoices/Nano/nano.pdf
	* http://www.cis.upenn.edu/~KeyKOS/NanoKernel/NanoKernel.html
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http://en.wikipedia.org/wiki/Microkernel#Nanokernel reports:

The term NanoKernel or PicoKernel historically referred to:
* A kernel where the total amount of kernel code, i.e. code executing in the privileged mode of the hardware, is very small. 
* The term PicoKernel was sometimes used to further emphasize small size. The term Nanokernel was coined by Jonathan S. Shapiro in the paper The KeyKOS NanoKernel Architecture. 
* It was a sardonic response to Mach, which claimed to be a MicroKernel while being Monolithic, essentially unstructured, and slower than the systems it sought to replace. 
* Subsequent reuse of and response to the term, including the PicoKernel coinage, suggest that the point was largely missed. 
* Both NanoKernel and PicoKernel have subsequently come to have the same meaning expressed by the term MicroKernel.
* A virtualization layer underneath an operating system; this is more correctly referred to as a hypervisor.
* A hardware abstraction layer that forms the lowest-level part of a kernel, sometimes used to provide real-time functionality to normal OS's, like Adeos.
* There is also at least one case where the term nanokernel is used to refer not to a small kernel, but one that supports a nanosecond clock resolution

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Go to http://www.apple.com, click on the developer tab, search on nanokernel, there are 91 results.

	 :	''The Nanokernel and the 68LC040 Emulator are low-level Mac OS initialization components that were part of BootPowerPC code in previous CPU ROMs. They are now included in the Mac OS ROM Image.''

So, it seems it is an Apple specific term, with no currency elsewhere. The Apple usage of nanokernel refers to an extremely primitive OS layer that provided only interrupt control, no VM or OS services.

Hmmm... Google finds some current usage of the term by IBM, Sony and some others.


I've put some stuff up for ExoKernel from the MIT site, but I still haven't found anything for NanoKernel. I wonder if it's a real concept, or just an exaggerated MicroKernel.
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CategoryOperatingSystem