Hi Karen, (Bob: please see below...)

important snippet from

Support for LBA and FAT32 originally was a DRFAT32 device driver,
so in old DR DOS, you first have to boot from a FAT16 partition
which is entirely in the first 8 GB of your disk and less than
2 GB in size, I would assume. Also, FDISK may be limited, so you
better use something else than old DR DOS FDISK to partition...

In DR DOS 7.04 and newer, things were getting better, but it is
unlikely that you have that version. However, based on OpenDOS
7.01 source code, EDR-DOS implemented a free kernel with FAT32
and LBA support (version "DR DOS 7.01.08" of July 2011). Due to
license conflicts with the free improvements, DR DOS 8.0 and 8.1
have been discontinued, so DR DOS 7.03 (from the year 1999!) is
the most recent DR DOS. I strongly recommend EDR DOS instead:

(just get the binaries, otherwise you need source+patch+compiler)

Note that EDR DOS comes with very little extra software - simply
use the extra software of another DOS like DR DOS or FreeDOS :-)

Hi Bob,

> I wonder what the brandand firmware revisions the harddrive(s) in 
> question are and whether or not they have a size-limiting jumper 
> connected. Doesn't such a jumper, in combination with hardcoded BIOS 
> settings, control the cylinders-heads-sectors that "the DOS" flavor 
> sees? And doesn't DOS itself need a device driver in order to talk

The last time that I saw such a jumper, it limited the
size to 32 GB to avoid crashes with broken BIOSes. Also,
some drives came with software to limit them to 128 GB
to avoid yet other compatibility issues. Unless you have
a VERY old BIOS (early 1990s) you do not need drivers:

The BIOS will support sizes up to 128 GB using LBA, or
in newer BIOS versions even up to 2 TB and more. Older
DOS versions only support CHS which is where "geometry"
(cylinder head sector) matters. If at all possible, use
DOS versions and partition types with LBA, as those do
not need to worry about geometry. For example MS DOS 4
does not support LBA, so you must use CHS and geometry
must match between BIOS *and* partitioning *and* DOS.

The BIOS will usually select some default with many
(240, 254, 255?) heads for big disks, to get as much
of the disk as possible in the first 1024 "cylinders"
but you still do not get further than 8 GB. So if you
must use CHS, pretend that your whole disk is smaller.
Even MS DOS 4 can then use up to 2 GB per drive letter
but do not get too close to 2048 MB or it will fail.

Really old (also early 1990s, 1980s) BIOS versions do
not support geometry settings above 16 heads, so you
would need "dynamic drive overlay" or "ontrack" style
"drivers" (actually installed as sort of boot loader)
to get beyond 500 MB (0.5 GB).

That said, a normal FreeDOS with FAT32 support can use
the first 2 TB of your disk as long as you use LBA FAT32
type partitions. You can even make one partition of that
size if you do not want to use several drive letters...

Using SSD is no problem for DOS at all, only the size
matters, the BIOS supports it all. If DOS would KNOW
that the disk is SSD, it could get a bit more speed.
Also, modern harddisk and SSD allow parallel access to
gain speed, but DOS is not multitasking things anyway.

Note that DOS drivers like UIDE allow faster data transfer
in cases where the "driver" built into the BIOS is slow.
So DOS drivers for disks do exist, but are not essential.

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