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Can't Create Partitions after DOS install

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First post, by Choux69

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Hello. I have a 6Gb hard drive and I used it to install DOS 6.2. During the install process, I chose to create and use a principal DOS FAT 16 partition with max size and the max I could choose was 472 Mb. That leaves a lot of empty space on the HDD. I wanted to use this empty space to create a 2nd partition and store files but FDISK won't give me the option to create it. When I try to create an extended partition, FDISK says there is not enough space. I tried to use a couple of other partition manager software (not so many available running under DOS...), but I can't fix this issue. It seems that the capacity of my HDD has been permanently reduced to 472 Mb. Any idea? Thanks.

Reply 1 of 12, by weedeewee

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verify that your disk is properly set up in the bios, and actually being identified to the system as a 6G disk. Since it seems that at the moment the system only sees 512MB

http://web.inter.nl.net/hcc/J.Steunebrink/bioslim.htm

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Reply 2 of 12, by Choux69

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Thanks for the reply. Yes the full HDD capacity is detected by the BIOS. See the clip screen of HWINFO. I also added the clip screen of FDISK when I attempt to create an extended partition.

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Reply 3 of 12, by Jo22

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Hm, that's weird. 🤔 The advices from our fellow Vogons users are fine.

Traditionally, there's the 504MB limit of old BIOSes and the 8GB limit (Large model, E-CHS).

And for DOS:
- 32MB (FAT12 or old FAT16, DOS 3.x),
- 2GB (max. partition size without patching; DOS 5/6)
- 8GB maximum HDD capacity (DOS 5/6)

Here's a chart that I drew.
Re: 512mb CF card cylinder values ?

However, there are also BIOSes with known HDD limits.
Edit: That link was also mentioned by weedeewee. 😎
http://web.inter.nl.net/hcc/J.Steunebrink/bioslim.htm

If you can, please run some more diagnostic programs.
Maybe there will be an inconsistency at some point. 🤷‍♂️

I recommend trying these:
MSD
CheckIt (CMOS information part)
SYSINFO (Symantec and/or Central Point versions)
IDEDIAG (Re: IDE disk-on-module + 386)
NSSI (very good)
DR. HARDWARE

Alternatively, you can try using XFDISK.

Or patch MS-DOS 5.00 for big HDDs. It really works.
Re: Intel VS440FX refuses to boot DOS 6.22 from detected SSD
Re: Browsing a harddisk under DOS without using BIOS routines (INT13H)

Or experiment with MS-DOS 7.1.
It also has FDISK (just dont use support for big HDDs/FAT32).

Good luck! 🙂🤞

PS: Are you from France? I'm asking, because I'm from Germany.
I could theoretically send you a spare EPROM pre-programmed with XTIDE Universal BIOS if nothing works.
It then can be installed on an network card, for example. 🙂

Edit: I forgot to mention.. The BIOS and the Setup Utility in a PC are two separare programs.
The Setup Utility is just like a DOS program on an EPROM which can show the correct data, even though the BIOS routines themselves don't support them.

Edit: I forgot. There's also DR DOS, Novell DOS 7 and PTS DOS/Paragon DOS.
Maybe their FDISK programs can help you.

They can be found at Winworldpc site, but I can't provide you with a link.
This forum doesn't support using them from such sources, also.
I merely mention this for testing purposes, so you can create yourself a bootable system disk with FDISK/FORMAT/SYS etc.
Similar to how Windows itself used to provide a bootable DOS diskette for troubleshooting.

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Reply 5 of 12, by weedeewee

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The HWINFO utility seems to,i'm assuming, just read the data directly off of the harddrive. Which in this case will be utterly useless. Sometimes useful, sometimes annoying utilities. (I think the author is also on this board 😉 )

What matters at this point is how your BIOS sees the harddrive. So, press del to enter your bios or whatever key you need to press and verify how the drive is set up in the BIOS.

Heck, you know, giving as much information about your system as possible would be nice.
like brand/model /version of your mainboard, amount & type of ram, which vga, which floppy drives, which other isa/pci/... cards are in the system.
It all makes it just a little bit easier to pinpoint the exact cause of your troubles. Without it we just have to guess, ask more questions and overall watch time go by waiting for the answers.

Enjoy ! 😀

Also, there's another annoyance I've noticed with booting later dos version, where Dos takes info from the existing partition table and uses it to override the bios info...
In that case, erase the existing partition, reboot, try again, ie create partition. if <=512MB, check BIOS.

Right to repair is fundamental. You own it, you're allowed to fix it.
How To Ask Questions The Smart Way
Do not ask Why !
https://www.vogonswiki.com/index.php/Serial_port

Reply 6 of 12, by dormcat

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Choux69 wrote on 2022-06-19, 13:26:

Thanks for the reply. Yes the full HDD capacity is detected by the BIOS. See the clip screen of HWINFO. I also added the clip screen of FDISK when I attempt to create an extended partition.

Have you tested the HDD on a modern computer? If so, what have Disk Management or similar tools shown you?

Reply 7 of 12, by Choux69

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So here is the information:
- MB = PC Chips M912 v1.7
- BIOS = AMI but I will check the version
- CPU = 486DX2-66
- 16 Mb RAM
- HDD = Quantum Fireball CX 6.4 Gb (see attached)
- Graphics = Trident TVGA 8900CL
- IO card = MIO TK82C863/865
I will send a picture of the BIOS screen tomorrow but I could autodetect the HDD and the geometry settings automatically set by the BIOS match the figures in the attached document

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Reply 8 of 12, by Malik

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I believe Smart Boot Manager has the option to enable the interrupt 13h to enable the full size of the hdd.

You need to install it as the boot manager in that system, where it resides in the MBR and takes care of allowing resources to the OS.

One of the links to SBM

5476332566_7480a12517_t.jpgSB Dos Drivers

Reply 9 of 12, by jakethompson1

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Sounds like the BIOS may not have LBA translation mode enabled. See what disk geometry MSD (comes with DOS 6) says for drive C:. LBA translation would trade fewer cylinders for more heads. The DOS<->BIOS interface can only handle 1024 cylinders. Translation pretends there are more than 16 heads to accommodate the cap on cylinders. You will have to reinstall after enabling LBA.

Reply 10 of 12, by Choux69

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Hello. update... No picture but hard drive was properly recognized by BIOS. I tried to hook up the HD to a modern computer via USB and create a partition with Minitool Partition Wizard ... When I re-hooked the HDD to the 486 Motherboard ...disaster... All directories and files were messed up...So I had to erase the DOS active partition and reinstall DOS 6.22 from scratch. That being said, "Jakethompson1" was right... LBA was not activated in BIOS so far. So I activated it before the new DOS install and was able to extend my primary DOS partition to 2047 MB and create an Extended DOS partition to 2047 MB. So I now use 4Gb out of the 6GB of the HDD. I don't think I can create a 3rd partition for the empty space with FDISK but that's much better than before! Thanks all. Really appreciate the willingness to help from Vogons members.

Reply 11 of 12, by jakethompson1

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Choux69 wrote on 2022-06-20, 18:18:

Hello. update... No picture but hard drive was properly recognized by BIOS. I tried to hook up the HD to a modern computer via USB and create a partition with Minitool Partition Wizard ... When I re-hooked the HDD to the 486 Motherboard ...disaster... All directories and files were messed up...So I had to erase the DOS active partition and reinstall DOS 6.22 from scratch. That being said, "Jakethompson1" was right... LBA was not activated in BIOS so far. So I activated it before the new DOS install and was able to extend my primary DOS partition to 2047 MB and create an Extended DOS partition to 2047 MB. So I now use 4Gb out of the 6GB of the HDD. I don't think I can create a 3rd partition for the empty space with FDISK but that's much better than before! Thanks all. Really appreciate the willingness to help from Vogons members.

You should be able to create a bigger extended partition than that and additional "logical drives" (up to 2GB each) within the extended partition.

And yeah, generally disaster strikes if you try to move hard drives between machines with these old BIOSes/MS-DOS versions without repartitioning.

Reply 12 of 12, by maksymke

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I just had a similar problem - dos 6.22 installed on a 500mb partition and was unable to create an extended partition, even though fdisk was showing full HDD as 8GB

Instead of installing dos from the scratch with updated LBA settings, I just connected this HDD via ide-USB adapter, did backup (it only was like 200MB of files, so…) and only expanded existing fat16 partition to 2GB using partition magic on newer PC

Damn thing worked and it only took like 5 minutes with the hardest part being putting drive back to the crowded and cable tight 486 case

All files and system are intact and booted straight up

I hope it saves a lot of time for whoever will find himself in such situation!