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HimemSX, another HimemX variant (Announce)

posted by Zyzzle, 23.10.2020, 04:37

> > I compiled HimemSX with JWASM and it works, with interesting results.
>
> I have not tried this. Would it even work on a "lowly" 4 GB RAM laptop??
> Though it does remind me of CandyMan's similar
> EMS64 hack
> from a few years ago (2016).
>
> > I also patched the included RDISKSX.COM to allow the creation of up to a
> > 4095M ramdrive, from 2047M. Above 2048M, the ramdrive is created as
> FAT16
> > with the 64-kb cluster size. Beyond 4GB for ramdrive is impossible
> without
> > a FAT32 ramdrive for DOS and / or sector size > 512 bytes.
>
> Who was it that first supported 64 kb clusters in FAT16, was it NT 4.0?
> (Well, FAT32 wasn't added to NT until Win2k, right?)
Correct, but MS-"DOS" 7.1 does support 64-kb clusters just fine for me, as evidenced by the fact that I was able to create a 4GB ramdrive, read and write to it without errors, with a max filesize of 0x7FFFFFFF

>
> > Of course, it is impossible to write a file of >2047M because of the
> > signed 32-bit limit in filelength. Or, is there some patch to DOS
> > which will allow the creation the file to its 32-bit unsigned
> > maximum value of 4096M-1 byte?
>
> I could be wrong, but I believe Win9x (not sure when) supported 4 GB files
> in limited ways, e.g. you had to create them with int 21h, 716Ch only.
> DJGPP "beta" 2.04 had some support for this, allegedly. Unfortunately, I
> don't think NT (XP, etc.) ever supported those sizes (at least not for DOS
> APIs). Also, FreeDOS (IIRC) still doesn't either due to "signed long" bugs
> (hence max file size is still 2 GB there even on FAT32).
Yes, I remember the Win98 DOS API *does* support reading and writing of unsigned long integer filesizes between 2GB and 4GB. Why are "signed long" integers even necessary for filesize lengths? You can't have a negative filesize, so we've wasted the high bit, thereby depriving ourselves of "2-4 GB" filesizes access in DOS. I've wondered why FreeDOS hasn't fixed this bug. Implement int 21h and 716Ch access without a signed long limit. This could work even on FAT16 drives with 64-kb clusters.

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