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about to fix the "final" doslfn bug (Announce)

posted by Richard, 13.04.2022, 11:24

> > > The real question is why it's so slow (the RAM drive in particular).
> >
> > Perhaps it's not related to doslfn at all. It might be a BIOS bug,
> setting
> > up memory beyond 4GB as "uncachable" via MTRRs. I remember that, when
> > HimemSX was introduced, another member of this forum (Zyzzle?) had such
> > problems.
>
> Yes, that is correct. Some of the memory beyond 4GB is "uncacheable" via
> MTRRs and only showing a 50 mb/sec transfer speed on an i5-8250 system.
> That system doesn't enable MTRRs for some reason, and it slowed memory
> transfers down by a factor of about 500x. No system that I've tested above
> a 5th Gen core i5 system has successfully cached memory in MTRRs.
> Limitation of Intel's? BIOS limitation? I can't figure why this feature has
> been disabled or crippled.
>
> When HimemSX was tested on a system which does cache memory > 4GB via
> MTRRs, the memory speed was something around 10 GB / sec or greater on an
> core i5 5600 laptop. This laptop would also properly cache MTRRs via
> RayeR's MTRRLFBE utility while my core i5-8250 more recent laptop doesn't
> (executing MTRRLFBE wc lfb freezes the system).


I am willing to try same on my HP laptop with i7-4810MQ 32GB RAM (laptop manufactured 2015 and latest BIOS updates installed).

Where to get, how to use MTRRLFBE?

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