Jeff Isaac cineveggie.lists at gmail.com
Wed Feb 27 14:00:54 UTC 2008

On Feb 27, 2008, at 6:42 AM, Pete French wrote:

> "So the SMAP problem is that in the one BIOS I looked at, the SMAP  
> BIOS call
> only works from real mode.  Even if invoked from virtual 86 mode,  
> the BIOS
> call fails.  FreeBSD only calls the BIOS SMAP call from virtual 86  
> mode both
> in the loader and in the i386 kernel.  The fix is quite complicated  
> and
> involves rewriting the boot code to invoke BIOS calls from real mode  
> rather
> than virtual 86 mode."

Forgive me if this has already been asked, but I'm in the process of  
trying to teach myself some of the basics for the loader and boot,  
etc... on the powerpc port. I realize that this is platform specific  
and probably has zero bearing on anything I code specifically (since  
I'll have firmware to doodle with, not BIOS), BUT, from a general  
knowledge perspective, what advantages does virtual 86 mode have over  
real mode? Essentially, why did the FreeBSD project choose the virtual  
implementation? More portable? Easier to write? None of the above?  
Thanks! :)

- Jeff

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