28-bit LBA BIOS and 48-bit LBA XP - Can I use my 160GB hard disk safely?

[JS]

I recently upgraded my notebook with a 160GB hard disk. However in BIOS I
see only 137GB. I know it is because the BIOS is only so-called '28bit' LBA.
The notebook is of 4 years old and there will be no more BIOS update.
When I install XP (SP2) on this HD, I still see 160GB in XP. I heard it is
because the driver in XP SP2 (atapi.sys) is 48-bit LBA already so it can
recognize and access all 160GB disk.
But does this mean I can ignore the BIOS limitation and fully utilize 160GB
in XP? I also heard some people with similar HD upgrade suffered data loss
or system destruction because as something in the system doesn't support
48-bit, when writing to disk, it wraps back to first tracks and destroys
MBR, boot sectors etc. But I don't know whether it was because BIOS didn't
support 48-bit.
So my question is, with 28-bit BIOS, can I safely use 160GB disk with XP
Sp2?
I read many articles, including Microsoft ones, that state that besides the
OS 48-bit LBA support, BIOS must also support 48-bit LBA. But I also heard
that, BIOS is only active when booting up the PC, once it passes to OS, it
should be the OS that manages the disk. So, even though in BIOS I see only
137GB, it should not affect OS activities as long as OS supports 48-bit LBA.
So I am a bit confused: As OS can recognize 160GB, why BIOS matters? In what
situation can a 28-bit LBA BIOS destroy a 160GB disk?
I heard that some people say 'as long as the midpoint of the partition falls
below 137GB, the BIOS will be able to boot from that partition' because the
midpoint is where the MFT mirror is stored. But in XP the MFT mirror is
stored at the end of partition?

 

[Rich Barry]

Rt Click MyComputer>select Manage>Storage>Disk Management. Rt click
the Unallocated Space and select create Logical Partition (drive). That
should take care of
the remaining Drive Space. You will wind up with two partitions C: and D:

 

[JS]

That's not what I ask. I know how to partition disk. Auctually I already
partitioned this disk. My worry is whether my 28-bit LBA BIOS will screw up
my data.

 

[John John]

I wouldn't trust it and to tell you the honest truth I don't know how
Windows can properly see all of your disk if the BIOS cannot see it.
There are two necessities or requirements for Windows XP to properly
identify and use hard disks larger than 137GB. One is that you have at
least SP1 installed and the other is that the BIOS be 48-bit LBA aware.
I have never heard of one working without the other. The only way
around the BIOS requirements would be to place the disk on an
independent third party controller. I'm not sure what is going on with
your pc and why it seems to defy the above 2 requirements.

John

 

[JS]

Yeah, in XP I can see 160GB, but in BIOS it reports 137GB. Now I only
partitioned the first 137GB to use, left 20+GB tail not touched. So far
there is no problem but I really want to make use fof that left space.

 

[JS]

However, I met cases that sometimes BIOS cannot recognize a disk but it
appears in Windows. I don't know if you also have such experiences. So,
somehow Windows can see disks beyond BIOS, though I don't know how/why.

 

[JS]

However, I met cases that sometimes BIOS cannot recognize a disk but it
appears in Windows. I don't know if you also have such experiences. So,
somehow Windows can see disks beyond BIOS, though I don't know how/why.

 

[Ken Blake]

I recently upgraded my notebook with a 160GB hard disk. However in BIOS I
see only 137GB. I know it is because the BIOS is only so-called '28bit'
LBA.

How do you know that? How do you know that it's not the lack of SP1 or SP2,
which would have the same effect?

The notebook is of 4 years old and there will be no more BIOS update.
When I install XP (SP2) on this HD, I still see 160GB in XP.

Then it would seem that the BIOS is *not* the issue. If if were, Windows,
even with SP2, could not see the full 160GB.

I heard it is because the driver in XP SP2 (atapi.sys) is 48-bit LBA
already so it can recognize and access all 160GB disk.

You need *both* to be able to access the full size of a drive that large:

1. A motherboard with a BIOS and controller that supports 48-bit LBA (or
alternatively, an add-in controller card that does).

2. At least SP1 of Windows XP.

But does this mean I can ignore the BIOS limitation and fully utilize
160GB in XP? I also heard some people with similar HD upgrade suffered
data loss or system destruction because as something in the system doesn't
support 48-bit, when writing to disk, it wraps back to first tracks and
destroys MBR, boot sectors etc. But I don't know whether it was because
BIOS didn't support 48-bit.

I've never heard of such an issue. As far as I know, if either of the two
items I cited above is missing, you can not get the full drive size. If both
are present, you *can* get the full drive size, without a problem.

So my question is, with 28-bit BIOS, can I safely use 160GB disk with XP
Sp2?
I read many articles, including Microsoft ones, that state that besides
the OS 48-bit LBA support, BIOS must also support 48-bit LBA. But I also
heard that, BIOS is only active when booting up the PC, once it passes to
OS, it should be the OS that manages the disk. So, even though in BIOS I
see only 137GB, it should not affect OS activities as long as OS supports
48-bit LBA.

Not correct. Windows can only see what the BIOS reports to it. *Both* are
required.

 

[John John]

Maybe someone else has an explanation for what is going on with your
notebook but I would leave it as you have it now. The partition and
data below the 137GB boundary is safe with the 28-bit LBA BIOS. Using
anything above that might be asking for trouble.

John

 

[John John]

I have never heard of that. Like Ken said in his post, without both
requirements Windows should not, or will not, properly see all the disk
space. Maybe your BIOS is 48-bit LBA aware, maybe you have a setting in
the BIOS that isn't quite right but that doesn't affect Windows... I
just don't know what is going on with your pc.

John

 

[JS]

How do you know that? How do you know that it's not the lack of SP1 or
SP2, which would have the same effect?

===> Because I see 137GB in BIOS, that XP is not yet boot up, not to mention
Sp1/2.

Then it would seem that the BIOS is *not* the issue. If if were, Windows,
even with SP2, could not see the full 160GB.

===> This is one thing I wonder. The fact is I see '137GB' in BIOS, but in
Windows it sayus 160GB.

You need *both* to be able to access the full size of a drive that large:

1. A motherboard with a BIOS and controller that supports 48-bit LBA (or
alternatively, an add-in controller card that does).

2. At least SP1 of Windows XP.

===> I read many articles that speak of the same, but seeing my case, I
don't know why I need BIOS. I heard once that BIOS only acts during booting
up, when it passes to XP, it is XP that manages, so BIOS is not that
important when XP boots up. Now I just don't know who's right.

I've never heard of such an issue. As far as I know, if either of the two
items I cited above is missing, you can not get the full drive size. If
both are present, you *can* get the full drive size, without a problem.

===> Again, I checked many times, BIOS says 137GB, but in XP disk manager,
it says 160GB. I partitioned first ~130GB, and the left can be seen there
'non-used'.

Not correct. Windows can only see what the BIOS reports to it. *Both* are
required.

===> But how can my case be explained then?

 

[JS]

From the other JS in this newsgroup

My older PC (call it 'Old') will not support 48Bit LBA, however I recently
removed my 80GB primary drive and replaced it with a 160GB drive that was on
another PC (call it 'New') that does support 48Bit LBA. I formatted the
first 137 GB using the 'New' PC and then installed it on the 'Old' pc. Used
Ghost to restore the image to the 160GB drive (I created the image before
removing the 80GB drive from the 'Old' pc).

After booting to Windows my 'Old' pc (using Disk Management) showed the
drive as 160GB with the first 137GB partitioned, the remaining drive space
as 'Unallocated' but Disk Management will not give me an option to partition
and format the unallocated space. My BIOS does not display any useful
information (tried changing bios settings but this provided no additional
info) about drive size so I can't unfortunately provide any help on BIOS.

JS

 

[JS]

In my case, I partitioned the 160GB by 8GB (the XP system), 40GB and 60GB
(data), and left about 43GB. I can see it as 'unallocated' and I can
partition it (but I do not do so).