video drivers, agp, mtrr, and write-combining

Alice Corbin
2005-04-20T21:12:49Z

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