Some senseless babbling from George White to Mike Ruskai
on 11-19-99  10:04 about fdisk /query...

 GW> Hi MIKE,

 GW> On 17-Nov-99, MIKE RUSKAI wrote to JONATHAN DE BOYNE POLLARD:

  table

 JDBP>> It's worth noting, by the way, the very last entry given by FDISK.
 JDBP>> This indicates that there are 5MeB of space on her second physical
 JDBP>> drive that aren't assigned to any partition.  The irony is that with
 JDBP>> the scheme chosen by Linda's guru, this space is completely unusable,
 JDBP>> since no more partitions can be created on the disc.  (Although one
 JDBP>> wonders why the fourth primary partition "J:" was created short like
 JDBP>> this.  Perhaps a side effect of creating the partition using a hex
 JDBP>> editor on the partition table and doing the arithmetic incorrectly ?
 JDBP>> (-:)
 
 MR> It might have been FDISK that did the bad math.  One of my drives has 7MB
 MR> of empty space at the beginning, and just a single logical drive defined.
 MR> FDISK did it, not me.

 GW> I don't think so, what you're seeing on your system is a different
 GW> problem (FDISK peculiarity :-( ). When FDISK is told to create an
 GW> extended partition on a drive with no primary defined, it creates a
 GW> minimum size, hidden, inaccessible, primary partition on the drive at
 GW> the start. Why? - don't ask me...

Will Honea pointed out what should have been obvious - the convention is to
have partition tables on cylinder boundaries.  I can't see any reason why
this is necessary, but it just is.

Since a logical drive isn't defined in the partition table of the MBR (the
one at sector 0 of the physical drive), the next partition table would have
to be at the next cylinder boundary, which in the case of the drive in
question is 7MB away.

Partitions themselves start on track boundaries, though, so a primary
partition would leave only one track worth of unused space between the MBR
and the partition's first sector.  The sector count between the partition
table that defines it, and the actual start of a partition is stored as
"hidden sectors" in the BIOS parameter block, retrievable by a
DosDevIOCtl() category 8, function 63 (DSK_GETDEVICEPARAMS) call.

Mike Ruskai
thannymeister@yahoo.com


... Best way to dispose of the Borg: Give them Windows 3.1x

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