Programming an OS(Kernel and all)

Okay, I've been prowling the internet for a while now, searching high and low for some good tutorials, and, believe it or not, I've found some pretty good ones. The only problem is that most of them are lacking in describing WHY you do such-and-such one way as opposed to another.

Any pointers, tutorials, or tips from the pros out there?

OP here,
One or two I've found in the past include these:

http://www.osdever.net/bkerndev/Docs/intro.htm

and

http://www.osix.net/modules/article/?id=359