Re: [Freedos-user] hard drive question?

[Ralf A. Q. <Fr...@gm...>]

At 06:38 PM 11/13/2012, Michael B. Brutman wrote:
>I wanted to be able to dual boot my machine (a PCjr, 1983) to both
>operating systems.  DOS 3.3 uses an earlier variant of FAT16, which is
>only good up to 32MB.

Well, that's because this was a "true" FAT16, with up to 65535 
sectors of 512 bytes each, indicated by a partition type of 04h. 
"True" FAT16 because the sector count in the BPB is a 16 bit value.

>The FAT16 that everybody else is familiar with is more correctly 
>called FAT16B, and that allows for partitions up to 2GB.

Never heard the term "FAT16B" before, I remember that Compaq (who 
came up with the enhancement in their MS-DOS 3.31 version) used the 
term "Big FAT", using a partition type of 06h.
The partition limit of 2GB also applies only for DOS and early 
Windows 95, using a cluster size of 32KB. Windows NT (3.5+ IIRC) 
allowed for 64KB clusters, raising the limit for a FAT16 partition to 4GB...
Also, this is FAT implementation is using a 32bit value for the total 
sector count in the BPB, which makes it incompatible with earlier DOS 
versions (and hence the new partition type, preventing earlier 
version to even recognice those partitions)

>I think that 8GB is more than enough for any DOS system I'm ever going
>to run ...

+1

Ralf