ADEOS is the Adaptive Domain Environment for Operating Systems.

See:

http://www.opersys.com/adeos
ftp://ftp.opersys.com/pub/Adeos/adeos.pdf

ADEOS is "an extensible and adaptive environment which can be used to enable the sharing of hardware resources among multiple operating systems or among multiple instances of the same operating system". Basically, it's a NanoKernel which sits on top of bare hardware (x86 only, at the moment) and provides a transparent VirtualMachine environment for hosted OperatingSystem''''''s. ADEOS is RealTime (it's hard not to be, when you do as little as ADEOS!), so it can support RealTimeOperatingSystem''''''s.

ADEOS works by managing interrupts using an InterruptPipe, in which hardware interrupts are captured and then passed on to each of the hosted OperatingSystem instances in turn, with various cunning bits of flim-flammery to keep everything working properly. OperatingSystem''''''s which know about ADEOS deal with it directly, but those which do not are forced to run in a virtualized environment, contained by the CPU protection mechanisms; they are supposed to be unable to tell the difference between this and a real bare-metal environment.

There is a difference between ADEOS as described in the paper and as implemented; the version in the paper can work with ''unmodified'' monolithic OperatingSystem''''''s, whereas the implemented version (release 1) needs minor modifications to the interrupt-handling code of OperatingSystem''''''s which run on top of it.

Terrifyingly, ADEOS is implemented as a linux KernelModule, and so it is actually loaded ''after'' linux itself, and can be ''unloaded'' while linux is still running.

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CategoryOperatingSystem (although it's not really an operating system)