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Dif. MTRR WC setting behavior under v86-question for Japheth (Developers)

posted by RayeR(R) Homepage, CZ, 31.12.2018, 17:09

> I have no idea how this could be "fixed" in Jemm. I vaguely remember that
> the address ranges in the MTRRs are physical addresses, aren't they?

Yes, all this adresses - LFB base returned by VESA info and MTRRs are physical.
There's one more thing - caching modes (Write combining, etc.) are also affected by PAT (Page Attributes Table) and I know that PAT has higher priority than MTRR ranges (if the same area is defined as WC in MTRR and WB in PAT, then WB wins). My MTRRLFBE changes only MTRRs and don't touch paging tables. Maybe there is some difference how CWSDPMI, DOS4GW and JEMM handles paging tables (if they touch them) and how physical address is mapped to linear address...

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DOS gives me freedom to unlimited HW access.

 

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