According to what I'm reading, FAT16 was introduced in DOS 3.
So, I'm guessing that DOS 2, which would only know of FAT12, does not 'understand' the existing FAT16 partition on your hard drive.
Initial FAT16[edit]
On 14 August 1984, IBM released the PC AT, which featured a 20 MiB hard disk and PC DOS 3.0.[24][25] Microsoft introduced MS-DOS 3.0 in parallel. Cluster addresses were increased to 16-bit, allowing for up to 65,524 clusters per volume, and consequently much greater file system sizes, at least in theory. However, the maximum possible number of sectors and the maximum (partition, rather than disk) size of 32 MiB did not change. Therefore, although cluster addresses were 16 bits, this format was not what today is commonly understood as FAT16. A partition type 0x04 indicates this form of FAT16 with less than 65536 sectors (less than 32 MiB for sector size 512).
With the initial implementation of FAT16 not actually providing for larger partition sizes than FAT12, the early benefit of FAT16 was to enable the use of smaller clusters, making disk usage more efficient, particularly for large numbers of files only a few hundred bytes in size, which were far more common at the time.
MS-DOS 2.x hard disks larger than 15 MiB are incompatible with later versions of MS-DOS.[26] A 20 MiB hard disk formatted under MS-DOS 3.0 was not accessible by the older MS-DOS 2.0 because MS-DOS 2.0 did not support version 3.0's FAT16. MS-DOS 3.0 could still access MS-DOS 2.0 style 8 KiB-cluster partitions under 15 MiB.
Nope, I don't agree with that. The first type of FAT format used for hard disks was that of the 12-bit FAT12 partition, which is still in use today for floppy disks. This type of FAT allows a maximum of 4,086 clusters of 4,096 bytes, for a total of 16,736,256 bytes per disk....(theoretical partition size is 32 MiB for FAT12)...
Nope, I don't agree with that. The first type of FAT format used for hard disks was that of the 12-bit FAT12 partition, which is still in use today for floppy disks. This type of FAT allows a maximum of 4,086 clusters of 4,096 bytes, for a total of 16,736,256 bytes per disk.
Then prove it to us. Get out your DOS 2.x and try it on your 20MB drive. I suspect you can accomplish this by forcing a larger cluster size. But with the default size of 4K the limit is 16MB. I think you can get up to 32K (I forget how to do this) and that would give you up to 128MB size (along with other headaches that I have also forgotten the details about).... But I know that DOS 2.x supports partitions that exceed 16MiB.
In article <704@nicmad.UUCP>, brown@nicmad.UUCP writes:
> The only way you can have PC-DOS 2.10 run 20MB hard drives is if:
> 1. You run partitioned drives with two 10MB partitions or
> 2. You butchered the drive to fool DOS
> As PC-DOS 2.10 stands, it is not able to format 20MB hard drives as 20MB.
Sorry, but the computer I'm using to answer this note has a 20MB Seagate
disk with a single PC-DOS partition 20 MB in size. It was formatted by and
is running PC-DOS 2.1. I'm glad I didn't know better, or I might never
have tried to use it this way. I did no butchery of any kind on the drive.
The only ugly side effect is that the minimum file size is 8 KB instead of
the 4 KB on a 10 MB disk.
Has anyone else done it this way?
You are right in saying that PC-DOS 2.10 will NOT support a 20MB
hard disk directly. It is because the format command will only
support a 10MB hard disk.
Everex Systems (who sell mostly Seagate drives), include a software
patch for the format routine in PC-DOS 2.1, which is called LFORMAT.
This patch allows you to set up a 20MB hard drive for PC-DOS 2.1
We have been putting 20MB hard disks on PC-DOS 2.1 for quite some
time.
Personally though, I still agree with you -- PC-DOS 3.10 is the
way to go if you are pursuing larger mass storage.
Aloha,
--
Jonathan Spangler
{ihnp4,vortex,dual}!islenet!jons
"On Thursday, the world came to an end."