🚀 go-pugleaf

"Jeremy Brooks" <jem@datasecurity.co.uk> wrote:

>I see a lot of partitions where the partition table and the boot sector
>sector length appears to be either 1 or 2 cylinders longer than the actual
>disk (as detected by the BIOS).
>
>Perhaps this is a miscalculation by the Windows/DOS install routine.
>
>I see this an awful lot when fix hdds (i.e. partition table data against
>BIOS CHS values).
>
>Example:
>
>int 13h get disk info returns
>
>995,31,63     (disk has 2007936 sectors)
>
>but partition table says
>
>128    6    0,1,1 - 996,31,63     63      2009889
>
>and boot sector bpb.huge_sector_count = 2009889
>
>or
>
>128    6    0,1,1 - 997,31,63     63      2011905
>
>and boot sector bpb.huge_sector_count = 2011905
>
>Could it be that this disk has this problem and the disk has become full and
>scandisk or DOS is trying to r/w these non-existent clusters (i.e. the last
>or penultimate cylinder).
>
>This may or may not be the source of the problem, but in any event I would
>be interested to hear of anyone who knows why this happens (and it happens
>an awful lot).
>
>Kindest regards,
>
>Jem

I've never noticed that.

On this computer the two agree: 620,63,63. The BIOS params are
622,64,63, so there is one cylinder of slack. 

FDISK calls int 13 ah = 8 (or the equivalent extended function if for
LBA) before it fills in the partition table, so it would seem to be
most likely a bug in some version of FDISK. I'll have to keep an eye
out for that one.

Bob