Robert C Wittig wrote: > Yes, Jeff Duntenamm explains this quite clearly in his newest > book, but he continues, by saying that it is best to at least > study it well enough, before moving on to 32 bit protected mode, > to understand *why* it sucks, so that you (me, in this case) will > not just be parroting other peoples' opinions. Besides, now that > I have mastered the basic understanding of what it is all about, > it is not really all that hard to understand, or use... just put > the 1st half (segment addy) into the appropriate segment > register, and the second half (the offset), into the IP register. Agreed! if you know what you are doing it aint a big deal. I think it all boils down to jumps. The short jump command is only two bytes, the standard three, which is +/- 32k of wherever you are, which moves a window of addresses along as the software runs and changes the IP register. And if you do wanna use the long jump, you can go anywhere.
I can see where this might create problems with higher order languages like C, cause you dont know how far away any given jmp is, and if the insertion of more code moves it beyond the 32k limit... With assy, you can make a judgement on how often a subroutine gets called, and decide whether it should be more carefully placed. I can see as well that these kinds of optimizations, on modern platforms that run so fast with such large address space are not really all that useful. You could just as well design an os with a flat address space where every call has to be double or quad word; nobody cares if every call wastes a handful of bytes, there's plenty more where that came from. To unsubscribe from SURVPC send a message to [EMAIL PROTECTED] with unsubscribe SURVPC in the body of the message. Also, trim this footer from any quoted replies. More info can be found at; http://www.softcon.com/archives/SURVPC.html
