Do you mean FAT16 or FAT32? FAT16 is fairly standard for DOS (according to wikipedia, DR-DOS included FAT16 support since 3.31), but FAT32 is only supported in OpenDOS (DR-DOS became Novell DOS, and then Caldera OpenDOS).
Also, keep in mind that some versions of Windows are designed to not run well on non-Microsoft DOS (see this article). It seems that public releases don't exhibit that behaviour, but maybe you'll have other problems (maybe someone that uses DR-DOS+Windows can help you).
And no, games won't run any better using DR-DOS, because:
- Games don't execute much DOS code (maybe only data loading ), so they won't be affected by a faster DOS (I do NOT say that DR-DOS is faster/more optimized than other DOS).
- Most time, games are executing their own code. Changing the underlyng DOS won't change game code at all, so you won't get any optimizations. The only way to get a game optimized for pentium processors is recompiling it.
- DR-DOS had to support any PC from 8088 to Pentium. Writing Pentium specific code in DOS core would prevent that.
- The only thing in DOS that can benefit games is freeing up memory. I don't know if DR-DOS could get more free memory than MS-DOS, but I don't think it was so important for 486/Pentium games. Except some strange cases (like Comanche or Ultima games), they needed less base memory but became XMS/EMS hungry.
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