In article <>, Luke Skywalker
<> wrote:
> On Thu, 09 Dec 2004 05:56:08 -0500, (Paul) wrote:
> >Before filling the disk with valuable data, make sure that
> >Windows truly is 48bit LBA ready.
>
> Thx a lot for the tip. This is pretty scary :-( Is there a utility
> from either MS, Asus, or Seagate that could perform this test instead
> of going through the procedure you gave?
>
> I'll google to understand why this is even a problem to begin with
> (too old motherboard?)
>
> Thx again
> Luke.
It is the difference between 26 bit addressing mode and 48 bit
addressing mode. Imagine an address that uses all 26 bits, like
11 1111 1111 1111 1111 1111 1111. Now, try to make that hardware
write to one sector past that number (which would be the
128GB location plus one sector). All the digits become zero,
and the carry bit is dropped. The hardware gets
00 0000 0000 0000 0000 0000 0000, and the first sector
of the disk is now corrupted. If the path to the hardware
only supports 26 of the sector address bits, then the "rollover"
happens at the 128GB (binary) mark.
That is how it happens.
I have read one account of someone who used their large
disk, and lost all their files about 3 months after they
started using the disk. Based on the description of the
symptoms, it would seem the user had just crossed the
128GB mark.
You could accelerate the test, by positioning a partition,
so that the 128GB mark falls within a small partition.
Filling that partition alone, will cross the 128GB mark,
and reduce your test time. So, say you position a
partition at 127GB (binary, mind you, be careful of
the math) and the partition is 2GB long. Then, you
would only have to copy 2GB worth of files, to test
the crossing of the magic address.
The way the disk drive manufacturers calculate gigabytes,
the magic sector address works out to 137GB in decimal
gigabytes (10**9 bytes = 1GB). If you count a gigabyte
as 1024x1024x1024, then the magic mark becomes 128GB
or 2**37 bytes. A sector contains 512 bytes or 2**11.
2**37/2**11 = 2**26, the 26 bit sector address.
Testing the whole disk is easier than figuring out
how to set up the partitions :-)
HTH,
Paul