[caption id="attachment_41" align="alignright" width="300" caption="MacBook Pro Legacy Edition."][/caption]
It is so funny, having the year 2008 and being forced to take of stuff like this:
enabling the A20-gate to access more memory than usual a few hundred years ago, then reading through the interrupt documentation ( my favorite is actually "Read light pen position", int 10 ) to discover that actually all of it is completely outdated and that new standards were built on top ( VESA, e.g. ).
But believe me, it is really interesting to learn that stuff, it gives you a really new way of seeing a computer.
Anyway, i stuck at the A20 line. It's there for well-documented legacy reasons ( I toyed with the idea to link to wikipedia, but dropped it, everybody should be able to access wikipedia :-) ) and survived even the Apple PPC-Intel transition, so now its part of my mac. In fact its nothing really disturbing, just a few lines of code, and I think it shouldn't be considered a major flaw. It's just funny.
Another thing that will maybe amuse you is the interrupt descriptions. Its just so not up-to-date, rather fits in a museum than on a mainboard, but well, still supported. Except maybe the light pen, though I like the idea.