Partition Parameters
The Dell Utility partition is really an ordinary FAT16 partition, but the partition-type
indicator in the partition table has been changed from 06h to DEh (hexadecimal notation,
or 0x06 and 0xDE).
(Note to self: the FAT16X partition type 0f 0Eh will work just
as well as 06h here. However, to boot the Utility partition the Dell bios seems to
expect the partition will be below cylinder 1024, so the partition itself cannot
really be FAT16X.)
The size of the partition is not critical, and seems to be around 31-64 MB on most systems,
with files occupying less than 10 MB of this space.
Although a FAT16 partition would otherwise be recognizable to Windows, using a non-standard
partition-type indicator in the partition table causes it to be ignored when Windows is
booted from the main partition. This, of course, would be the way Dell likes it--Dell doesn't
expect the user to tamper with the Utility partition when using the computer normally.
Using any non-standard partition-type indicator will effectively hide a partition like
this, but I suppose Dell uses DEh because it's cute (DE = DELL, get it?) and because
nobody else is using it.
(Note to reader: the common way of hiding a 06h or 0Eh partition is
to change it to 16h or 1Eh.)
That means Dell can design their bios code to look for the DEh marker with a reasonable
expectation that it's one of their utility partitions.
The DE partition is formatted FAT16 and boots DOS.
Older utility partitions boot MS-DOS 7.0 (the version of DOS from Windows 95).
Newer utility partitions boot DRMK 4.1 or 8.0. This is Dell's own variation of DOS,
and appears to be functionally similar to MS-DOS.
(Note to reader: the purpose of DRMK may be to avoid paying licensing
fees to Microsoft, not to add extra DOS functions.
DRMK apparantly stands for "Dell Real-Mode Kernel".)
Other DOS versions, such as DR-DOS or FreeDOS, may also work just as well here.
Note that when the DE partition is booted from the bios boot menu, it does not change
anything in the partition table. Even though the DE partition is booted as though it
were an active FAT16 partition, the partition-type indicator is still DEh and the Windows
partition is still indicated as active in the partition table.
The two states of the DE partition--sealed and unsealed--are differentiated by different
config.sys and autoexec.bat files. These startup files are designed to automatically
follow one of two different scenarios when the partition is booted. The sealed scenario
runs the seal.exe program, while the unsealed scenario runs the delldiag.exe program.
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