DOS ain't dead

What is the max number of floppy drives I can have on FreeDOS under VirtualBox ?

How many CD-ROMS can I have ?

Hard Drives ?

USB Drives ?

Right now this is all hypothetical conjecture.

Just thinking that it might be useful knowledge one day.

> What is the max number of floppy drives I can have on FreeDOS under
> VirtualBox ?
>
> How many CD-ROMS can I have ?
>
> Hard Drives ?
>
> USB Drives ?
>
> Right now this is all hypothetical conjecture.
>
> Just thinking that it might be useful knowledge one day.

26 floppy/hard disk/optical/network/usb drives per DOS machine or whatever is set in your LASTDRIVE var. Note, each drive takes some bytes of RAM whether or not it is mounted or available to DOS.

You can have drive letters from A: to Z: in DOS (if you set your LASTDRIVE to Z) but you can only have 2 floppy drives in FreeDOS.

The UDVD2 driver supports up to 4 SATA or IDE CD, DVD or BluRay drives, but our SHSUCDX (similar to MSCDEX) only supports ISO9660 format. DVD or BluRay cannot be used via SHSUCDX if they are formatted with another filesystem.

You can have up to 8 SATA or IDE (PATA) harddisk, SSD or similar fixed disks cached and udma/ultradma accelerated with the UHDD driver, with an arbitrary number of partitions on them. Actually you can have a bit more, but it will depend on how many floppy drives you have and whether you use SATA or PATA etc.

FreeDOS itself supports only MBR style partitions, not GPT style partitions for fixed disks (SSD or harddisk) yet, but Bret Johnson's USB drivers support both already We support FAT12, FAT16 and FAT32, with CHS and LBA style addressing, with disk sizes of up to 2 Terabyte as long as your BIOS supports that. Larger disks would require GPT partitioning or sectors larger than 512 byte, neither of which are supported by the FreeDOS kernel yet. MS DOS 6 is far more limited, but Windows 95/98's MS DOS 7 also supports large disks and partitions, as does EDR-DOS.

No idea how many simulated floppy, harddisk or CD/DVD drives and controllers you can have in VirtualBox. Some very old DOS versions supported up to 4 floppies and had E: as the first harddisk drive letter. FreeDOS is not one of those. You will probably not have UDMA in VirtualBox and because it can use the cache of your host system (Linux, Windows etc.) a DOS cache such as UHDD is less important, but still nice to have.

Note that both UHDD, UDVD2 etc. and DOS itself cache disk contents, so when you tell VirtualBox to virtually insert a different disk, check whether DOS and the DOS drivers properly got notified of the disk change. And do not write to your disk images from Linux or Windows at the same time while VirtualBox is running and using them, because this will probably fail to trigger any content change notifications visible for DOS!

> How many CD-ROMS can I have ?
>
> Hard Drives ?
>
> USB Drives ?

---
FreeDOS / DOSEMU2 / ...

The number of different drives you can have is not a simple answer. There are simply too many ways to do things.

While booting things are VERY different than what can happen after you've booted. You can, for example, boot from a floppy (A: or B:) or a hard/USB drive (C:) or a CD (which may create a RAM disk of some sort) or even boot virtually across a network. There may be other ways to boot as well.

When first booting, only A: and B: can be floppies. After booting, any drive letter can be a floppy. E.g., my USB drivers (at least in their current state) never assign a USB floppy to A: or B: but assign it to some other drive letter. There are also utilities like SUBST and JOIN that let you assign drive letters in all kinds of unusual ways if you want. Those utilities will even let you assign more than one drive letter to the exact same device (which, believe it or not, is sometimes very useful -- I actually use that feature all the time).

In DOS, the main thing you need to worry about is making sure you put a LASTDRIVE=Z in CONFIG.SYS so you can assign drive letters from A-Z, though exactly what kind of device each drive letter is assigned to is not consistent. Also, later versions of MS-DOS would let you put LASTDRIVE=32 in CONFIG.SYS which would allow 32 drive "letters" (though accessing the drive "letters" higher than Z: is very problematic and usually not worth the grief it causes). I don't know if any other versions of DOS besides MS-DOS will let you do that or not.

> Also, later versions of MS-DOS would let you put LASTDRIVE=32
> in CONFIG.SYS which would allow 32 drive "letters" (though accessing the
> drive "letters" higher than Z: is very problematic and usually not worth
> the grief it causes). I don't know if any other versions of DOS besides
> MS-DOS will let you do that or not.

https://en.wikipedia.org/wiki/Drive_letter_assignment

> Some Novell network drivers for DOS support up to 32 drive letters
> under compatible DOS versions. In addition, Novell DOS 7, OpenDOS 7.01,
> and DR-DOS 7.02 genuinely support a CONFIG.SYS LASTDRIVE=32 directive
> in order to allocate up to 32 drive letters, named A: to Z:, [:, \:, ]:,
> ^:, _: and `:. (DR-DOS 7.02-7.07 also supports HILASTDRIVE and
> LASTDRIVEHIGH directives in order to relocate drive structures into
> upper memory.) Some DOS application programs do not expect drive letters
> beyond Z: and will not work with them, therefore it is recommended to
> use them for special purposes or search drives.
> ...
> Windows 9x (MS-DOS 7.0/MS-DOS 7.1) added support for LASTDRIVE=32
> and LASTDRIVEHIGH=32 as well.