OK, another printf() produces the following information:

	gm->fbbase = 0x8347400, gm->fboff = 0x400

So, adding these two numbers together gives us 0x8347800, which as Jason
points out will always make pmap_extract() return something with low order
bits set to 0x800.

Given that my video card's frame buffer physical address is 0xfd000400, I
rather suspect that the gm->fboff is correct;  of course, this means that
the gm->fbbase is incorrect.

So, since this worked before (as recently as April 28th), does any one
know what's changed?  :)

On Sun, 25 May 1997, Jason Thorpe wrote:

> On Sun, 25 May 1997 13:03:51 -0700 
>  greywolf@starwolf.starwolf.com (Missing - presumed fed.) wrote:
> 
>  >  * For some strange reason, the pmap_extract() call returns a value of
>  >  * 0xfd000800 while mac68k_vidphys contains 0xfd000400.  The latter value
>  >  * agrees with what the booter passes in.
>  >  * 
>  >  * So, does anyone know why the pmap_extract() return value is 0x400 higher
>  >  * than it (apparently) should be?  :)  Is it maybe some sort of "rounding
>  >  * up to the next page boundary" error?
>  > 
>  > Well, what's pagesize() on a mac68k?  If it's 1024, then rounding is
>  > not the problem.
> 
> Page size on a Mac is 4k.
> 
> Paul - What virtual address are you passing pmap_extract()?  If it ends
> in "800", then you're going to get that back from pmap_extract().
> It's returning:
> 
> 	page_pa | (va & PGOFSET)
> 
> Jason R. Thorpe                                       thorpej@nas.nasa.gov
> NASA Ames Research Center                               Home: 408.866.1912
> NAS: M/S 258-6                                          Work: 415.604.0935
> Moffett Field, CA 94035                                Pager: 415.428.6939
> 

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