I've got the hint that I can speed up access to VESA graphics memory on P4s by setting a MTRR.
Before I dig into the Intel Manuals, has anyone a sample how to enum the current MTRRs and possibly to set them?
Now I wrote a small tool which display current variable MTRRs and allows to modify the values. Works in win9x (and on native DOS with HX) only.
IIRC f0dder wrote some driver to access MSRs in ring3. Don't know why, but I can't find it on his site.
I guess I should upload it to http://f0dder.reteam.org - but the ring3 MSR service is attached to this post. It doesn't contain any info for accelerating video access, though... the actual MSRs will depend on your CPU (though I think the MSRs are the same for all CPUs that supports it). A few DOS VESA demos might support it, or you can probably find info in linux drivers.
it's clear to me what to do to speed vesa video memory access, dont need any more infos.