I think it's a limit of the FAT32 filesystem.

Hello,

Thanks for the reply. It seems like FAT32 has a theoretical maximum partition size of 2TB. https://www.partitionwizard.com/convertpartit … size-limit.html

The drive is partitioned to 200 gigs, and I am able to use it. I'm just trying to determine whether something in DOS 7.1 is not going to like it.

Thanks!

Unfortunately DOS 7.1's built-in disk utilities doesn't seem to work well with drives that are too large (>137GB).

You'll probably need to use some powerful partitioning tools to achieve such, like GParted.

Not sure if DOS 7.1 behaves correctly with large drives, though. It needs knowledge about related parts in IO.SYS to figure out.

Thank you for the reply.

Amazingly the built in DOS partitioner (fdisk) and the built in formatter (format) both happily created a 200 gig FAT32 partition. I did not have to resort to gparted.

I agree that a fundamental understanding of IO.SYS would be necessary to really know whether DOS will have problems at some point. I have about 85 gigs of stuff on there (out of 200), and DOS is happily working with a DOS version of MAME. I was just hoping that someone had tried it and could point out issues that I might experience. For example, maybe storing over 128 gigs is going to give me issues?

Thanks!

I have not been able to get the MS-DOS 7.1 FDISK to see more than 137 GB. Same results with FreeDOS FDISK, interestingly.

Can Ranish or XFDisk go beyond the Int48 limit?

Hi @keenmaster486,

Does your motherboard setup tool indicate how big it thinks the hard disk is? It sounds like if your motherboard only does 24 bit LBA (edit: the site referenced is off by 4 bits, so a 28bit LBA is more likely what you have as: 2^28 * 512 = 137gig), then it is limited to the size you mentioned: http://www.largeharddrivesupport.windowsreinstall.com/

I must have support for a larger LBA (likely 48 bit) in my P4, as the the motherboard setup util correctly identifies the drive as 200 gig.

I searched for Philscomputerlab videos to try and see if he addresses this for a pure DOS setup, but have not found any.

Kind regards,
Bill

coldturkey wrote:

Does your motherboard setup tool indicate how big it thinks the hard disk is? It sounds like if your motherboard only does 24 bit LBA, then it is limited to the size you mentioned: http://www.largeharddrivesupport.windowsreinstall.com/

Ah, this indeed may be the issue. It is a 200 GB drive. Not that I'm complaining; Windows 95 can't even use more than 32 GB on a partition anyway 🤣

356.92 gig
I used the hddguru fdisk to partition
took 40 minutes
the cdu version of 7.10 ,not the one from windows.

DOS relies on the BIOS for hard disk access. So it will have the limits of the BIOS, unlike Win9x, which talks to the hardware directly.

I have not been able to get the MS-DOS 7.1 FDISK to see more than 137 GB. Same results with FreeDOS FDISK, interestingly.

BIOS limitation. 137 GB is LBA28 limit.

I let the modded fdisk make the partition

Norton disk doctor in dos 7.10 shows it as a 357G drive
the 246m is a usb cf card fat32

BIOS limits will apply, for sure, but assuming the BIOS supports it, DOS still has to be able to handle various different structures without screwing up.

Tthere's *A LOT* of code in DOS that never got tested with large drives. For example, are you using CHS or LBA? If CHS, heads==255 will cause problems, which is why most BIOSes will limit the # of heads to 255, or heads==254 (0-indexed). I would guess this has something to do with code that used an 8-bit data type, and at some point there's a calculation that added 1 to that value, which overflowed to 0 and resulted in a geometry that has no valid meaning. There are TONS of opportunities for screw-ups like that. DOS may support 32-bit sector counts, but do all the intermediate calculations for FAT use 32-bit math? Do all the byte calculations use 64-bit math? Could very likely happen that, somewhere, there's a variable that overflows under some rare condition and results in a barrier that doesn't seem to fit any of the known limits. Maybe it depends on the cluster size. You never know.

So, will it work? Probably. Reliably and without issue? No telling. I can't think of any time where it was meaningful to have that much space available to DOS. 😉 Try it and let us know -- for science!

First, your BIOS needs to support matured EDD INT13H and LBA48.
Next, you must have the patched FDISK from Win98 or Win98SE somehow even if you are not aware of it. Otherwise, the FDISK can only see 32GB at most. This is real, I came across this several times in the past.
With both, you are literally only limited by FAT32 2TB limit for DOS. I believe it will be fine if you stick with the standard DOS disk utilities such as SCANDISK. By Win98, almost all 3rd-party utilities vendors were on their last breath. There is no reason to use anything else that come with the OS itself.

fdisk refused to make a new partition,said the disk was full.
I used aomei partition assistant in win 7 to make a new fat32 partition 357G like the 1st.
DOS booting on C wouldn't recognize the new drive.
That was rude.
I used hirens boot cd 15.2 parted magic to make partition 2 lba like the 1st.
Then dos recognizes the 2nd drive.
The last 1.2 Tb of the 2Tb drive I made a ntfs partition for vista or win7.
DOS norton disk doctor running on c:
gets the size right

Quick piece of advice: DO NOT run anything older than XP with larger than a 128 GB partition. Even if you get it to boot and "work", if you put more than 128 GB of data on it, the FAT table will get corrupted and you will lose all your data. There were some hacks to get around this, but if your hack gets reverted, your FAT table will get corrupted and you will lose all your data.

This goes for Windows 95, 98, and even Windows 2000. Windows XP was the first Microsoft OS to properly support large partitions.

EDIT: If you want to test this, you can create the partitions with a Linux boot disk using gparted. Then boot to DOS 7.1, and copy more than 128 GB to the partition, and see if it gets corrupted.

Win2k won't even install,it says partition corrupt or not formatted.

If the BIOS is limited to 32gb (a real limit i have hit more than once), win2k could likely notice that any partition past that point results in corruption. Win2k did have a registry mod that enabled 48bit LBA IIRC, but ecen that is no help if the BIOS is limited i think.
If I had a smaller hdd available, id use that. some even had a jumper for "32gb clip" so that it didn't use the space above 32gb for machines like this. Some boards have buos updates to use up to 120gb, but many dont.

If this hdd is all you have, pull all the partitions and make a 31.9gb partition. After that everything should at least be able to install an os.

I tried a single 2TB partition (on a 4TB drive) using DOS 7.1 a couple of years ago. Partitioned using the dos FDISK from Winme and dos Format from Winme. (win98 versions didn't work). Partition type was '0Ch' - FAT32 with LBA.
It worked fine with no data corruption. This was using a intel P965 chipset motherboard with a bios that supported 48bit LBA. The drive was filled with 1TB of data and then I copied that 1TB under dos7.1 to the remaining free 1TB of space on the drive. Then pulled out the drive put it in win7 pc and checked for corruption with hashes. Unlike Dos6.22, Dos 7.1 supports INT 13h Extensions so unlike win98 will support 2TB drives without any corruption or need for device drivers. The only problem with corruption is if the BIOS itself has bugs which i haven't come across myself with Int13. This also works on a 486 with PCI slots if you use an ide controller that supports 48bit LBA.