XP SP2 & 48 bit LBA

[Philip Roberts]

Assuming your BIOS can handle large hard drives, does SP2 correct the
problem with 48 bit LBA or do you still have to change the registry key to
prevent possible corrupion beyond 137 Gb?

Many thanks

 

[Tom]

Assuming your BIOS can handle large hard drives, does SP2 correct the
problem with 48 bit LBA or do you still have to change the registry key to
prevent possible corrupion beyond 137 Gb?

Many thanks

Service Pack 1 took care of that in 2002, and anything SP1 has, is included
in SP2, as SP2 is all the fixes in SP1 plus anything that was made after
SP1's release.

 

[Timothy Daniels]

Service Pack 1 took care of that in 2002, and anything SP1 has,
is included in SP2, as SP2 is all the fixes in SP1 plus anything that
was made after SP1's release.

He asked specifically if you have to add/change a Registry key.
I have WinXP Pro installed with SP1/SP2, and the 48-bit LBA
key still doesn't exist in the Registry.

*TimDaniels*

 

[Anna]

He asked specifically if you have to add/change a Registry key.
I have WinXP Pro installed with SP1/SP2, and the 48-bit LBA
key still doesn't exist in the Registry.

*TimDaniels*

I take it the OP's basic question (rephrased) is, "If my motherboard's BIOS
supports large-capacity hard drives, i.e., disks whose capacity are > 137
GB, and I have installed SP2, is that all that's needed to support
large-capacity disks?".

And, of course, the answer to that is "Yes". There's no need "to change the
registry key to prevent ...". As long as the motherboard's BIOS supports
large-capacity disks, i.e., disks whose capacity is greater than 137 GB and
SP1 and/or SP2 has been installed, the full capacity of the disk will be
recognized. All motherboards that have been manufactured during the last
four years or so have this capability based upon my experience with a fairly
large number of them. Many of the older boards that didn't originally have
this capability have BIOS upgrades to include this capability.

A slight addendum to the above...
If the user installed a large-capacity disk at the time his XP OS did *not*
contain SP1 and/or SP2, then the system would recognize *only* 137 GB
(roughly) of that disk (we'll assume the BIOS recognizes large-capacity
disks). When he or she subsequently installs SP1 and/or SP2, the full
capacity of that disk will be recognized, *but*, the remaining capacity
beyond 137 GB (roughly) will be "unallocated space" which, of course, the
user can partition/format. So that at a minimum the disk will have at least
two partitions. Probably not an important consideration for most users who
will be multi-partitioning those large disks anyway.
Anna

 

[Tom]

He asked specifically if you have to add/change a Registry key.
I have WinXP Pro installed with SP1/SP2, and the 48-bit LBA
key still doesn't exist in the Registry.

*TimDaniels*

No, you don't need to make the change, unless one installed the a large disk
prior to installing the service pack 1 (unlikely since SP1 has been out for
almost 3 years now). But if the BIOS will already handle large drives, and
SP1-2 is already installed, then it is no issue. I have 2 160gig HDDs, and
never had to make the change with this PC, which came with SP1a.

No entries in my registry exist to show such a modification

 

[Timothy Daniels]

No, you don't need to make the change, unless one installed the a large disk
prior to installing the service pack 1 (unlikely since SP1 has been out for
almost 3 years now). But if the BIOS will already handle large drives, and
SP1-2 is already installed, then it is no issue. I have 2 160gig HDDs, and
never had to make the change with this PC, which came with SP1a.

No entries in my registry exist to show such a modification

That has been my impression also - that with a capable BIOS and
SP1 or SP2, no Registry changes or additions need be made. But
within just the past few days, a poster claims that the addition of a
Registry key must still be made to access locations on the disk
beyond the 137GB range.

*TimDaniels*

 

[Admiral Q]

Let's put it this way, I've not added it, and I have 2 internal 250GB and 1
external 250GB, all 3 formatted a max capacity of 233GB (base 2 versus base
10 issue here), none have shown no signs of data corruption mentioned by the
OP.

--
Star Fleet Admiral Q @ your service!
"Google is your Friend!"
www.google.com

***********************************************

 

[Timothy Daniels]

Thanks for the confirmation.

*TimDaniels*

Let's put it this way, I've not added it, and I have 2 internal 250GB and 1
external 250GB, all 3 formatted a max capacity of 233GB (base 2 versus base
10 issue here), none have shown no signs of data corruption mentioned by the
OP.

 

[Andy]

Assuming your BIOS can handle large hard drives, does SP2 correct the
problem with 48 bit LBA or do you still have to change the registry key to
prevent possible corrupion beyond 137 Gb?

Contrary to popular belief the BIOS is not critical, unless during the
boot process the disk has to be accessed past the 137GB boundary
(basically applies to primary partitions larger than 250GB)..
EnableBigLba is used only by Windows 2000. Run Disk Management and
look at the left side of the screen for each drive; if it shows the
full capacity of the drive, then the operating system will access the
drive correctly.

 

[Timothy Daniels]

;

Contrary to popular belief the BIOS is not critical, unless during the
boot process the disk has to be accessed past the 137GB boundary
(basically applies to primary partitions larger than 250GB).

Can you think of such a scenario? The MBR is usually right at the
start of the disk, and its boot code is loaded into memory for execution,
and similarly for the boot sector of the partition containing the OS.
If the boot sector and the OS are in a partition way up high on the disk,
the code loaded into memory would be accessing it, so it would seem
that a limitation in the boot sector code or the MBR code would be the
cause, not the BIOS. Yet the Dell Common Knowledge is that the BIOS
for my circa 1999 desktop has to be updated before it can do the 137GB
cha cha.

EnableBigLba is used only by Windows 2000.

Well, that explains why I can't find it in my WinXP's registry.


*TimDaniels*

 

[Philip Roberts]

The reason for my original post was this particular piece of information in
the Knowledge Base on the Maxtor website:

"Maxtor's Big Drive Enabler is a one step executable that enables support
for drives larger than 137 Gigabytes in Windows 2000 Service Pack 3 and XP
Service Pack 1. This utility takes the guess work out of editing the Windows
registry. The Big Drive Enabler fixes an operating system limitation. This
utility is needed anytime a Hard Disk Drive larger than 137 GB is connected
to the motherboard's ATA bus, regardless of any system BIOS that supports
48-bit LBA."

I am still struggling to get a definitive answer.

Philip

 

[Anna]

The reason for my original post was this particular piece of information
in the Knowledge Base on the Maxtor website:

"Maxtor's Big Drive Enabler is a one step executable that enables support
for drives larger than 137 Gigabytes in Windows 2000 Service Pack 3 and XP
Service Pack 1. This utility takes the guess work out of editing the
Windows registry. The Big Drive Enabler fixes an operating system
limitation. This utility is needed anytime a Hard Disk Drive larger than
137 GB is connected to the motherboard's ATA bus, regardless of any system
BIOS that supports 48-bit LBA."

I am still struggling to get a definitive answer.

Philip

Philip:
Struggle no more.

There are two basic requirements for the XP operating system to recognize
the full capacity of hard disks greater than 137 GB

1. The motherboard's BIOS must support large-capacity disks, i.e., disks
whose capacity is greater than 137 GB; and
2. SP1 and/or SP2 has been installed as an upgrade to the XP OS.

That's it. Nothing too terribly complicated about the basic requirements.
Some additional points...
a. Virtually all motherboards that have been manufactured during the last
four years or so have this capability based upon my experience with a fairly
large number of them. Many of the older boards that didn't originally have
this capability have BIOS upgrades to include this capability.
b. If the user installed a large-capacity disk at the time his XP OS did
*not*
contain SP1 and/or SP2, then the system would recognize *only* 137 GB
(approx.) of that disk (we'll assume in this situation the BIOS recognizes
large-capacity disks). When he or she subsequently installs SP1 and/or SP2,
the full
capacity of that disk will be recognized, *but*, the remaining capacity
beyond 137 GB (approx) will be "unallocated space" which, of course, the
user can partition/format. So that at a minimum the disk will have at least
two partitions. Probably not an important consideration for most users who
will be multi-partitioning those large disks, but something to keep in mind.
c. I *strongly* advise you *not* to install Maxtor's Big Drive Enabler or,
for that matter, any HD manufacturer's "drive overlay" program for the
purpose of "enabling" large-capacity disk support. As most computer repair
technicians will tell you, these drive overlay programs are curses. They
modify the hard drive in proprietary non-standard ways that by & by will one
day rise up and bite you. If your BIOS does not support large-capacity
drives and no BIOS upgrade for your motherboard exists to achieve this
capability, there's only one tried & true way to gain this capability --
purchase a controller card such as the Promise Ultra133 TX2 and install it
in your machine. They're simple to install and they do their job. Controller
cards such as these are reasonably priced -- the last time I looked online
vendors were selling them for about $35 or so.
Anna

 

[Philip Roberts]

Anna,

Thank you for taking the time to give such a detailed response. I will
struggle no more.

Philip

 

[Andy]

;


Can you think of such a scenario? The MBR is usually right at the
start of the disk, and its boot code is loaded into memory for execution,
and similarly for the boot sector of the partition containing the OS.
If the boot sector and the OS are in a partition way up high on the disk,
the code loaded into memory would be accessing it, so it would seem
that a limitation in the boot sector code or the MBR code would be the
cause, not the BIOS. Yet the Dell Common Knowledge is that the BIOS
for my circa 1999 desktop has to be updated before it can do the 137GB
cha cha.

Any code that is executed during the boot process does not directly
access the disk. Rather it uses BIOS interrupts to access the disk.
The MFT is placed in the middle of the NTFS formatted partition. The
file system of any partition whose MFT lies past the 137GB boundary
cannot be read during the boot process if the BIOS does not support
48-bit LBA. For a single primary partition, the size of that partition
is about 137GB x 2.

The setup program of Windows XP incorporating SP1 or 2 does not use
the BIOS to partition and format the disk, so it is able to partition
and format a 300GB disk as a single primary partition. However, once
it has copied the preliminary files to the disk and reboots, the
Windows XP installation will not boot up if the BIOS does not support
48-bit LBA.

 

[Timothy Daniels]

Any code that is executed during the boot process does not directly
access the disk. Rather it uses BIOS interrupts to access the disk.
The MFT is placed in the middle of the NTFS formatted partition. The
file system of any partition whose MFT lies past the 137GB boundary
cannot be read during the boot process if the BIOS does not support
48-bit LBA. For a single primary partition, the size of that partition
is about 137GB x 2.
The setup program of Windows XP incorporating SP1 or 2 does not use
the BIOS to partition and format the disk, so it is able to partition
and format a 300GB disk as a single primary partition. However, once
it has copied the preliminary files to the disk and reboots, the
Windows XP installation will not boot up if the BIOS does not support
48-bit LBA.

Are you sure that the MFT is placed in the physical middle of the
partition and not the LOGICAL middle? In a binary tree structure,
the root could very well be at the physical start of the medium's
address space. I searched through the on-line Microsoft knowledge
base, and I couldn't find any reference to the physical middle or
address space middle of the NTFS-formatted partition as being
the location of the MFT. There *were* one or two refs to the
*logical* middle, though.


*TimDaniels*

 

[Tom]

Are you sure that the MFT is placed in the physical middle of the
partition and not the LOGICAL middle? In a binary tree structure,
the root could very well be at the physical start of the medium's
address space. I searched through the on-line Microsoft knowledge
base, and I couldn't find any reference to the physical middle or
address space middle of the NTFS-formatted partition as being
the location of the MFT. There *were* one or two refs to the
*logical* middle, though.


*TimDaniels*

You have it correct partially as far a "logical center" but it resides in
the boot sector also, read here:
http://www.ntfs.com/ntfs-mft.htm

 

[Timothy Daniels]

You have it correct partially as far a "logical center" but it resides in
the boot sector also, read here:
http://www.ntfs.com/ntfs-mft.htm

OK. Now back to the original statement about the location of the
Master File Table. Does any part of it reside physically at the center
of the partition, or does it reside totally in the boot sector?

*TimDaniels*

 

[Tom]

OK. Now back to the original statement about the location of the
Master File Table. Does any part of it reside physically at the center
of the partition, or does it reside totally in the boot sector?

*TimDaniels*

Yes, it resides in the center, you can note this during a defrag (especially
good defragging programs). The link I gave you said specifically that it
resides there. "A duplicate of the boot sector is located at the logical
center of the disk."

Here is an example snapshot of a defrag analysis (hope you have high speed
internet), and note the color legend regarding the MFTs to the color scheme
in the main window.

http://home.insightbb.com/~guesswho192/MFT_example.JPG

 

[Timothy Daniels]

Yes, it resides in the center, you can note this during a defrag (especially
good defragging programs). The link I gave you said specifically that it
resides there. "A duplicate of the boot sector is located at the logical
center of the disk."

Here is an example snapshot of a defrag analysis (hope you have high speed
internet), and note the color legend regarding the MFTs to the color scheme
in the main window.

http://home.insightbb.com/~guesswho192/MFT_example.JPG

If the MFT must be in the middle of a partition or the middle of a disk,
it seems you're pointing out a problem of access by the BIOS of MFTs
in drives larger than, say 2x137GB. But all the BIOS does is load the
code in the Master Boot Record, which is at the bottom of the HD's
address space, and that executable code, using the partition table,
finds and loads ntldr. It would seem that the BIOS really doesn't have
to access anything higher than cylinder 0 on the disk.

*TimDaniels*

 

[Tom]

If the MFT must be in the middle of a partition or the middle of a disk,
it seems you're pointing out a problem of access by the BIOS of MFTs
in drives larger than, say 2x137GB. But all the BIOS does is load the
code in the Master Boot Record, which is at the bottom of the HD's
address space, and that executable code, using the partition table,
finds and loads ntldr. It would seem that the BIOS really doesn't have
to access anything higher than cylinder 0 on the disk.

*TimDaniels*

I am not pointing out any problems, this is simply how this functions in
NTFS formatted partitions

The BIOS only loads to what is designated the first boot device, after that,
it is up to the device to begin loading through the MBR. MBR and the MFT
have little to do with each other, and how the BIOS recognizes listings.