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DOS and 4 GB of memory (Users)

posted by marcov, 31.07.2008, 10:56

> I realize the whole 4 GB address space cannot be directly used in DOS in
> 32-bit systems because of virtual mapping, etc. The most I've been able to
> get HIMEM.SYS ver. 3.0 to see is 3328 MB. This is with an old 128-MB ATI
> Radeon 9200 card. Am I correct in assuming that reducing the total video
> memory will augment the total available DOS RAM? So using an old 4 MB or 8
> MB card would give me more addressable memory?
Not per se. A card can map more than it has memory.

The main culprit seem to be modern chipsets that require a full 256MB mapping.

PAE and memory remapping could be a solution, since under Dos, mostly only BIOS accesses the roms? Note that I haven't researched this, it is just intuitive.

Btw, what's the matter with all these new chipsets that come with big warning stickers "can't run win9x" ? Is this something only matters for support, or is it something major?

> I'm surprised the HIMEM.SYS even sees above 2 GB, and I was able to use HX
> DOS-extender to run Win32 apps like PIFAST 4.3, and utilize above & beyond
> 3 GB of memory.
Note that many programs, specially C ones doing pointer arithmetic might have problems when using address over 2GB.

> What about PAE -extensions in DOS to utilize > 4 GB memory on a 64-bit
> CPU?
A lot of older Xeons also support PAE. Not just 64-bit ones.

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