I'm considering making changes to a private version of FreeBSD that builds a single kernel with support for both PAE capable processors as well as those that don't have PAE support. (If you don't know what PAE means, it's OK; it just means you can safely ignore this post :-)
I'm wondering if anybody has any thoughts on this subject. Yes, I've thought deeply about the implications of the many constants wose values are derived from Page Directory Indexes (i.e., see the definition of the VADDR() macro and the variables defined in terms of it).
It's a really difficult task and so I'm also curious if the results of this project would be welcome in the standard FreeBSD tree.