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-   -   28 bit or 48 bit LBA Hard Drive? (https://www.askmehelpdesk.com/showthread.php?t=571797)

  • Apr 21, 2011, 05:16 AM
    mitchsc
    28 bit or 48 bit LBA Hard Drive?
    I was told that if I do a fresh install of the original Windows XP, I will create a 28 bit LBA hard drive, that cannot be changed to a 48 bit hard drive, even if I update XP to Service Pack 1, 2, or 3.

    After hours of reading, it is my understanding that 48 bit LBA hard drives are "manufactured" to that standard, and are not created by the operating system.

    At http://www.48bitlba.com/winxp.htm , it seems clear that if you start with Windows XP, and update to Service Pack 1, 2, or 3, you will have full 48 bit LBA addressing with your hard drive. You don't need to have the original Windows installation include SP1, 2, or 3.

    My BIOS is 48 bit LBA compliant, and I am using a Western Digital Caviar Blue 250GB Desktop Internal Hard Drive, 7200RPM EIDE 8MB Cache 100Mb/s 3.5" WD2500AAJB - OEM

    Can someone please confirm this?

    If I need a copy of XP SP3, I will have to purchase it, as opposed to doing my Service Pack updates from my original XP CD.

    Thanks...
  • Apr 21, 2011, 08:44 PM
    Scleros

    Please permanently stop listening to whoever told you that. One doesn't create a 28 bit or 48 bit hard drive during Windows installation. The issue is that the storage drivers in Windows XP prior to Service Pack 1 support 28 bit addressing. 48 bit support was added in SP1 (and later SP versions). The consequence of this is that if you attempt to install a pre-SP1 copy of Windows XP on a large drive, the operating system will only be able to access 137GB(128GiB) of it reliably until SP1 or later is applied. This can be a problem during a fresh installation if the drive is partitioned into a single partition that is larger than 137GB, or into multiple partitions that extend past 137 GB. The workaround is to partition the drive into a single partition less than 137 GB, finish installing Windows XP, install SP1 or later, and then either expand the partition to the full drive capacity using a partition editor or create another partition consuming the remaining capacity. Another method is to create an installation disc of Windows XP with SP1 or later already applied (process called slipstreaming) to allow creation of a large partition during installation.

    Related info at How to enable 48-bit Logical Block Addressing support for ATAPI disk drives in Windows XP.
  • Apr 22, 2011, 06:54 AM
    mitchsc
    Thank you so much for clarifying this. I spent hours yesterday reading and trying to understand it.

    My own version of a workaround has been to load XP, then SP1a, then SP3 on my original small HDDs, then after the installation is complete, I clone the entire installation over to my 250 or 320GB drives.

    This has always worked fine, but I became concerned after I was told that the drive was only operating at 28 bit (which made no sense to me since I was able to access the full drive capacity.

    Again, thanks for the clarification.

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