Re: [lwip-users] Port to 8086 Architecture.

[Kieran Mansley]

On Mon, 2007-02-19 at 11:37 +1300, David Empson wrote:
> On Saturday, February 17, 2007 3:55 AM, "Kieran Mansley" <address@hidden> 
> wrote:
> > On Fri, 2007-02-16 at 09:49 -0500, Robert Morse wrote:
> >> What I had to do was in the one section where the address compare in
> >> the pbuf_header() routine.  I had to change the if to call a function
> >> that created a linear address from the segment/offset then compare those
> >> address.
> >
> > It's not entirely clear from this what change you made, and whether it
> > is more widely applicable.  Could you supply a diff?
> 
> The 8086 and 80186 address memory using a 16-bit segment and 16-bit offset. 
> (This also applies to "real mode" in later 80x86 processors.) The segment is 
> multiplied by 16 to determine the physical memory address of a particular 
> "paragraph", then the offset is added. A segment by itself can be used as 
> the base address of a 64 KB memory area, but any address which is a multiple 
> of 16 within that area can be the start of a new segment, so segments can 
> overlap, and multiple combinations of segment and offset can refer to the 
> same memory location.

Thanks for the background and explanation - very helpful in
understanding the change.

Kieran