mach64 EXA bits

Ville Syrjälä syrjala at
Thu Aug 10 10:37:44 PDT 2006

On Thu, Aug 10, 2006 at 04:37:27AM -0400, Michael Lorenz wrote:
> Hash: SHA1
> Hello,
> On Aug 10, 2006, at 04:13, Benjamin Herrenschmidt wrote:
> >
> >>Not sure if that's what you mean but usually the framebuffer aperture
> >>offers two views to video memory and registers, one swapped one not.
> >
> >Not quite on newer chips. For example, on radeons, you have indeed 2
> >apertures, though they can be individually configured for different
> >swapping settings and to map the same or 2 different areas of video
> >memory. It's not that clear. Also, the swapper setting has to be
> >different depending on the pixel size you are accessing (no swap for
> >8bpp, 16 bits swap for 16bpp and 32 bits swap for 32bpp).
> Well, the subject says mach64, not Radeon ;)
> I'm clueless about Radeons but I did some hacking on mach64 chips like 
> Rage II, Rage Pro etc. and those are all-or-none swappers.
> >The problem is that EXA might manipulate, for example, 32 bits pixmaps
> >and 8 bits mask pixmaps in the same "aperture".
> >
> >I don't remember the details of how mach64 is or can be configured.
> I don't think there's much configuration regarding swapping at all - 
> the old ATI chips only have a split swapped / non-swapper aperture ( or 
> rather one BE and one LE view )

Actually both apertures support swapping and they can be configured 
independently. The lower aperture=LE, upper aperture=BE is just some 
convention mentioned in the mach64 docs. I guess it's useful if you're 
not using the auxiliary register aperture because then the registers 
are located in the lower aperture.

Ville Syrjälä
syrjala at

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