video drivers, agp, mtrr, and write-combining

From: Alice Corbin
Date: Wed Apr 20 2005 - 16:14:15 EST


I have a silly question.

I've noticed that some, though no all, video drivers add their video memory
to MTRR as 'write-combining' if both MTRR and AGP are configured in.

Is there a reason that all video drivers don't do this? Is it all would
benefit from write-combining memory, but that some simply haven't been
updated to take advantage of it? Or could write-combining actually be
detrimental to some video drivers? (And if the former, would it make
more sense to do the mtrr_add in a central location, say agpgart?)

Ali
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