[9fans] fdisk: reported number/size of cylinders changes

[Axel Belinfante <Axel.Belinfante@cs.utwente.nl>]

Something funny I noticed when using
fdisk on a new 80Gb Maxtor hard disk
(diamondmax plus 9).

When I used fdisk on the new disk,
it reported
	9809 cylinders of 8355840 bytes.

After making and saving a partition, quitting
and restarting fdisk reports
	39704 cylinders of 2064384 bytes.

(type script included at the end)

After zeroing (the start of) the disk,
fdisk again reports the 9809 * 8355840.

This surprised me.

In case it matters, I'm doing this on an old
Gigabyte motherboard (GA-686SGM), which had
a bios that did not support big disks, which
I flashed with a bios someone (unfortunately,
not gigabyte) patched for big disks.
Is this BIOS playing tricks on me?
(How much) should this worry me?

I did not (yet) repeat the experiment on a
different motherboard. (planning to do that,
but thought I'd mention it here first anyway)
It looks like I'm doing this with an older
kernel (Feb 18) but fdisk is recent.

Something else I noticed:
for this disk (80Gb maxtor diamondmax plus 9)
the ctl capabilities line does not contain dma
or dmactl; for the 80Gb maxtor diamondmax plus d740X
dma/dmactl are present in the ctl capabilities.

Confused,
Axel.



Just to be complete:

term% disk/fdisk /dev/sdD0/data
disk/fdisk: did not find master boot record
term% disk/mbr -m /386/mbr /dev/sdD0/data
term%  disk/fdisk /dev/sdD0/data
cylinder = 8355840 bytes
   empty                  0 9809        (9809 cylinders, 76.33 GB)
>>> a p1
start cylinder: 0
end [0..9809] 130
>>> t p1
new partition type [? for list]: FAT32
>>> p
'  p1                     0 130         (130 cylinders, 1.01 GB) FAT32
   empty                130 9809        (9679 cylinders, 75.32 GB)
>>> w
>>> q
term% disk/fdisk /dev/sdD0/data
cylinder = 2064384 bytes
   p1                     0 526         (526 cylinders, 1.01 GB) FAT32
   empty                526 39704       (39178 cylinders, 75.32 GB)
>>>