The OS dependencies of the core harmony VM should be very minimal.  In 
the case of Jikes RVM, there is a very thin layer of C code that 
interfaces to the OS (signals, system calls, bootstrap).  OS ports are 
fairly straightforward and very well contained within this interface.  
Therefore I don't see OS portability as a concern for the core Harmony 
VM.  Portability of the libraries is a bigger issue.

>Geir> To be clear, "using APR" and "writing in Java" aren't orthogonal, are
>Geir> they?  I would assume that we do need some boundary between the VM
>Geir> and the underlying OS/Hardware.
>
>You are correct.  Any VM will always need a way to call system
>functions somehow, and on Linux/Windows/etc, this means C ABI calls.
>Depending on the approach one chooses, some kinds of APIs are simpler
>to wrap than others, but I think this is not a major issue.
>
>Tom
>  
>