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Newbie- How to install DOS 2.1 / 3.1 on pentium133 / 4.3gb IDE drive

Farmall1938

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Nov 28, 2012
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Hey all- I'm trying to install PC DOS 2.1 (and separately MS DOS 3.1) onto a couple 4.3 gig drives...... but I can't seem to get DOS to recognize the drives. The PC DOS 2.1 does not have fdisk, so I was trying the MS DOS 3.1 as it does have fdisk. I used windows95 fdisk to wipe all partitions from the drive. Then reboot with DOS 3.1 and fdisk - it sees the drive and allows me to make a DOS partition.....but not a very large one- I think it said 500-something cylinders to use...... which is fine- I realize the drive can only be 20 megs or something..... But when I go to format- it says Format error. Is this even possible to do ? I'd like to have several hard drives with the different versions of DOS on them, just for grins..... I also have q-dos and DOS 5.0 and DOS 6.22. which I'd like to do similarly. Any pointers would be appreciated !


Farmall1938

Various Pentium and older MB/cards/memory/etc....nothing built yet- 2) HP 9920/dual floppy/ winchester drive (used to be a Brunning CAD system) sort-of works......LOL
 
In short -- you can't install DOS 2.1 on a hard disk. That's why there's no FDISK. 3.1 only supports 32 MB disks. You'll need DOS 3.3 or higher to support multiple 32 MB partitions. So your observations are correct. The DOS versions you have tried can't be used on the drive(s) you have tried to use them on.
 
In short -- you can't install DOS 2.1 on a hard disk. That's why there's no FDISK. 3.1 only supports 32 MB disks. You'll need DOS 3.3 or higher to support multiple 32 MB partitions. So your observations are correct. The DOS versions you have tried can't be used on the drive(s) you have tried to use them on.

Please don't tell my computer ... I have DOS 2.1 installed on a hard drive, it has FDISK.COM, and it is a documented command in the DOS reference manual.

DOS 2.1 uses FAT 12. You are limited to 15 or 16MB, and it has to be at the start of the hard disk. DOS 3.x is limited to 32MB using an older variant of FAT16, but it too insists on being at the start of the hard disk. If you try to move it out a little bit you will lose available space for your partition, or it will not partition it at all.

DOS 5 using the newer variant of FAT16 (FAT16B) is pretty flexible in all regards, except for the BIOS 1024 cyl limit.


Mike
 
Many late Pentium era BIOSes let the bootup drive be switched. This means that you can install an OS on each hard disk and whenever you want to change OS simply enter the BIOS and change the boot order. Restart the system and you should be in the OS you chose. With DOS's need to have the boot partition be at the front of the disk, separate drives are much easier than relying on boot managers and multiple tiny partitions that get hidden.

For DOS 6.22, setup is easy. With FDISK, create a primary partition of less than 2 GB. Then create an extended partition containing the rest of the disk. Inside the extended partition, create logical drives (each less than 2 GB) until you run out of disk space or get tired of creating logical drives. Then install DOS and format the drives as needed.

DOS 5 uses a similar procedure except that according to some of my sources, the primary partition and each logical drive has to be smaller than 512MB so you might have 8 logical drives.

With 2 disks after fully partitioning and formatting both, you might see something similar to the following:
DOS 6.22: Drive C (2 GB primary partition DOS 6 is installed on); Drive D (512 MB primary partition with DOS 5); DRIVE E (2 GB logical drive on the disk DOS 6 is installed on); DRIVE F (the rest of the disk DOS 6 is installed on, about 200 MB); Drives G through M would all be 512 MB logical drives on the disk with DOS 5; and Drive N with the remainder of the space of the disk DOS 5 is installed on.
DOS 5 won't be able to read the DOS 6 drives except for the small logical drive at the end. The highest drive letter would be L.

I would have to do some testing. I am not sure if DOS 2 or DOS 3 will be able to work with such a large disk. If you create a primary DOS partition of less than 16MB with DOS 5 or 6, DOS 2 or 3 should be able to format the partition if the drive can be worked with.
 
In short -- you can't install DOS 2.1 on a hard disk. That's why there's no FDISK. 3.1 only supports 32 MB disks. You'll need DOS 3.3 or higher to support multiple 32 MB partitions. So your observations are correct. The DOS versions you have tried can't be used on the drive(s) you have tried to use them on.

2.0 was the first official version of DOS that supported hard drives. What I don't recall is if 2.x allowed for partitioning or if it treated the hard drive as one big floppy. I seem to recall the latter was the case, but I can check.

Before someone calls me out on it, however--it was possible to incorporate hard disk support into DOS 1.1 at least if you had the DOS OEM kit from Microsoft. If you were an OEM, you were writing your own IO.SYS anyway, so you added hard drive support. You fought with all of the ugliness having to do with 12-bit FAT entries, however.
 
DOS 2.1 allows for partitioning. Otherwise, what is the purpose of FDISK?

It's the standard setup - 4 primary partitions. DOS 3.x (3.3?) introduced the extended partition.
 
There are always four partitions. DOS 2.x had four primary partitions, one of which could be for DOS. Later in the DOS 3.x series the concept of the extended partition was introduced. The extended partition can be created in place of one of the primary partitions, and in turn it may be further partitioned. The extended partition can have other DOS partitions in it, which will be seen as addition DOS drive letters. DOS 3.3 was the first to support multiple DOS drive letters via the extended partition.

There is a lot on the web about partitioning - nobody should have to rely on fuzzy memory. And every DOS manual has a section on setting up your hard disk.
 
DOS 2.1 allows for partitioning. Otherwise, what is the purpose of FDISK?

It's the standard setup - 4 primary partitions. DOS 3.x (3.3?) introduced the extended partition.
I don't know who's FDISK you are using but using FDISK with PC-DOS 3.2 there is only one partition of 32 MB or less allowed. DOS 3.2 FDISK does not allow for creation (or deletion) of a non-DOS partition nor does it allow for creation of a second DOS (extended) partition. As you said above, that came with 3.3.
 
But back in the days of DOS 2.x, were there even any hard drives larger than 15 MB available for PCs?
 
But back in the days of DOS 2.x, were there even any hard drives larger than 15 MB available for PCs?

Yes, there certainly were. I believe that Evotek even offered a 70MB drive at the time. (1983).

Mike is right about DOS 2.x and partitioning. 4 partitions and only one of which could be DOS. To make things even more confusing, partition sizes were shown in cylinders, not megabytes.
 
I can't find my copies of DOS 2.1 or 3.1 but I did spend a few minutes with an emulator and DOS 3.3. MS DOS 3.3 FDISK handled an emulated disk larger than 4 GB with no problems and successfully created a 32 MB primary partition and an extended partition that included 23 logical dos drives (each of 32 MB as well). I was a bit surprised because I remember that both OS/2 and Windows NT had problems with drives larger than 4 GB.

Someone else might have to verify if DOS 3.1 and DOS 2.1 could handle 4+ GB drives and create the lone tiny primary DOS partition.

Emulator was used because it is much easier to fake a needed size of disk instead of extracting correctly sized disks from the stack of spares.
 
A lot of the issues with hard disk support on early PCs lay with the BIOS interface. Standards said that 1024 cylinders, 16 heads and 17 sectors (142MB) was the limit for conventional CHS addressing when going through Int 13H. "Translating" hard disk BIOSes and RLL drives boosted that quite a bit, but revisions to the Int 13H API were really what did the trick.
 
OK- I have successfully created a 15mb active partition on a smaller drive.....I think it's about 120MB.......and have dos 3.21 bootable on it. Now I'm going to try a 15MB active partition on a 4.3gig drive. Thanks for all the help from each of you ! I plan to try this with the PC-DOS 2.1 later tonight..... There is no fdisk on the copy I have, so hopefully I can manage this...... because I think DOS 2.1 is a 12 bit file system, correct ???? I think someone mentioned this here also.....so I will post back with my questions and/or results ! It's been so long since I've played with this vintage stuff ! I booted a drive last week with windows 3.1 on it, and flashed back to my college days !!!! Wow what a blast from the past ! Thanks again, and I will keep ya posted !
 
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There was a bug fixed in DOS 3.3 where the boot sector code would sometime hang if the hard drive had more than 58 sectors per track:
Since most drives then were MFM and RLL with 17 and 26 spt respectively this problem was relatively insignificant.
 
Not to belittle the real experience but was there much of a reason not to run an emulator and run dos on that virtual system instead? Seems sorta underkill of an OS for a Pentium. Perhaps a 3rd party boot loader then you could also partition the rest for a modernish OS, linux or Windows 95.
 
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