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MTRR mystery (Announce)

posted by RayeR Homepage, CZ, 05.02.2012, 02:20
(edited by RayeR on 05.02.2012, 14:39)

> Do these help you further to troubleshoot the MTRR problems?
Yes. I can see that I may get various mess in MTRRs so it's not easy to make universal algo that will work on all systems. This should be job for BIOS to properly init thr HW... I also have to study Page Attribute Table and how to modify it. This may be better way. I read that it can override MTRR setting and allows fine granularity. It should be supported on PIII+. Surely I will make some further test version...

> What is a good option to benchmark MPLAYER, to test its absolute flatout
> speed, using 100% CPU power? Tried turning off VBE, and -speed, but are
> there other options?
You can try -benchmark -nosound and maybe disable vsync, then it should run unlimited speed. It worked for me and even with slowed down VESA I got ~4x faster speed.

UPDATE:
I found important note in intel SWDM:

11.11.4 Range Size and Alignment Requirement
A range that is to be mapped to a variable-range MTRR must meet the following
?power of 2? size and alignment rules:
1. The minimum range size is 4 KBytes and the base address of the range must be
on at least a 4-KByte boundary.
2. For ranges greater than 4 KBytes, each range must be of length 2^n and its base
address must be aligned on a 2^n boundary, where n is a value equal to or greater
than 12. The base-address alignment value cannot be less than its length. For
example, an 8-KByte range cannot be aligned on a 4-KByte boundary. It must be
aligned on at least an 8-KByte boundary.

So this means that fastvid set the mask wrong too! There are holes in the mask that may cause problems. In your case the range must be truncated to 16MB and it is possibe to setup additional ranges in size 8MB, 4MB, 2MB and so on to reach last 64kB block but it's wasting of free MTRRs as we have only 8 of them.
Page Attribute Table doesn't have such strict limitation - it needs only 4kB alignment.

---
DOS gives me freedom to unlimited HW access.

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