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Win95 OSR2 FAT32 notes

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Eric Gisin

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Oct 1, 1996, 3:00:00 AM10/1/96

There are a two new, but different features in SR2 fdisk.
This explains why only some people have problems with FAT16.
When you install Win95 SR2, it rewrites the MBR of disk 0,
but does not modify any partition types or boot records.

When you answer Y to the initial FAT32 question,
new partitions (of any size) are created FAT32, CHS or LBA.

When you answer N to the initial FAT32 question,
you either get a CHS FAT16 partition compatible with earlier DOS,
or a new LBA FAT16 or Extended partition if the BIOS supports LBA.
NT 4 will recognize these partitions, but other OSs may not!
You may have to use an older DOS boot disk or UNIX fdisk.

I did a quick peek at the new SR2 MBR.
The old one had two int-13s, the new one has half a dozen.
This is to support multi-sector partition boot records.
I'm not going to pursue this further, but if you do post something.

Here is some Microsoft doc (from OSR2's fat32api.hlp):

Partition Types

Value Description
PART_UNKNOWN(00h) Unknown.
PART_DOS2_FAT(01h) 12-bit FAT.
PART_DOS3_FAT(04h) 16-bit FAT. Partitions smaller than 32MB.
PART_EXTENDED(05h) Extended MS-DOS Partition. (CHS)
PART_DOS4_FAT(06h) 16-bit FAT. Partitions larger than or equal to 32MB. (CHS)
PART_DOS32(0Bh) 32-bit FAT. Partitions up to 2047GB. (CHS)
PART_DOS32X(0Ch) Same as PART_DOS32(0Bh), but uses Logical Block Address Int 13h extensions.
PART_DOSX13(0Eh) Same as PART_DOS4_FAT(06h), but uses Logical Block Address Int 13h extensions.
PART_DOSX13X(0Fh) Same as PART_EXTENDED(05h), but uses Logical Block Address Int 13h extensions.

Eric Gisin, Vancouver.bc.ca -- Windows/UNIX/Internet Consulting
http://www.webhaven.com/ericg/ mailto:er...@unixg.ubc.ca

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