Installing Windows NT on Large IDE Hard Disk Drives

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You may be unable to install Windows NT on a IDE drive larger than 504 megabytes (MB) or an IDE drive using more than 1024 cylinders (as configured in the CMOS settings). You may receive messages such as "STOP 0x0000007B INACCESSIBLE_BOOT_DEVICE" when NT reboots and starts the graphical user interface (GUI) portion of setup. If you are installing Windows NT from floppy disk, the problem occurs on Disk 9.

If you do get Windows NT installed, Windows NT may:

  • Not recognize the drive as the correct size. For example, it may see 500 MB free on a 504 MB drive.
  • Not recognize the drive even though it is recognized by other operating systems (such as MS-DOS).
  • See the full drive while other operating systems (such as MS-DOS) see only 500 MB of the drive.


This problem occurs when Windows NT Setup truncates the drive parameters to 1024 cylinders to support interrupt 13 compatibility. Interrupt 13 compatibility is required so the master boot record (MBR) can locate the boot sector. The boot sector then finds and loads the NT boot loader (NTLDR) and continues to load the operating system. NT uses interrupt 13 calls until a disk driver is loaded.

Historically, interrupt 13 compatibility has a limitation of 1024 cylinders. Secondary drives not containing the boot partition may not be limited to 1024 cylinders depending on the translation scheme used by the controller and drive.


To correct this problem:

  • Update your AMI BIOS to a version dated at 07/25/94 or later. These BIOS' support logical block addressing (LBA).
  • Purchase and install an IDE controller that has a built in translating BIOS. For example, the IDE controllers made by Buslogic and Promise provide translation functions so you don't need an updated BIOS. These are sometimes referred to as enhanced IDE controllers. Since the controller operates in place of the system BIOS it should work with any IDE drive currently available.
  • Partition the drive into partitions smaller than 500 Mb with MS-DOS FDISK and then install Windows NT on one of these partitions. The partitions must not exceed 1024 cylinders.

    NOTE: The above workarounds require you change CMOS settings and reformat your hard drive before you install Windows NT. Backup any data from your hard disk drive before making these changes.

  • Use Ontrack Disk Manager to partition and format the large IDE hard disk drive.

    For information on using Ontrack Disk Manager to do this, please see the following article in the Microsoft Knowledge Base:
    ARTICLE-ID: 124910
    TITLE : Using Ontrack Disk Manager to Support Large IDE Drives

More information

LBA allows the CMOS to provide sector translation so that the drive's physical parameters are hidden from the operating system. LBA does this by translating the drive's physical parameters into logical parameters, and then storing them in an enhanced parameter table. The value for the number of cylinders is set at the MS-DOS limit of 1024, and the value for the number of heads is increased. For example, a drive having 2048 cylinders, 16 heads, and 63 sectors per track could be reported as having 1024 cylinders, 32 heads, and 63 Sectors per track.

LBA uses the following algorithm for determining the level of translation to use:

   If the total number of sectors is less than 1032192 (FC000 hex), the
   drive is less than or equal to 528 MB; translation usually isn't needed.

   If the total number of sectors is less than or equal to 2164531 (210733
   hex), the drive is greater than 528 MB but less than or equal to 1056.9
   MB; the number of heads is set at 32.

   If the total number of sectors is less than or equal to 4329267 (420f33
   hex), the drive is greater than 1056.9 MB but less than or equal to
   2113.9 MB;  the number of heads is set at 64.

   If the total number of sectors is less than or equal to 86558534 (841e66
   hex), the drive is greater than 2113.9 MB but less than or equal to
   4227.8 MB; the number of heads is set at 128.

   If the total number of sectors is greater than 8658534 (841e66 hex), the
   drive is greater than 4227.8 MB; the number of heads is set at 255.

AMI technical support can be reached at (404) 263-8181.

You may purchase an updated BIOS by calling UniCore Software Inc. at (800) 800-2467. If you are using AMI BIOS, please provide, when calling, the information that appears in the bottom left corner of your screen when you boot your computer. This information identifies the core chipset.

The third-party products discussed here are manufactured by vendors independent of Microsoft; we make no warranty, implied or otherwise, regarding these products' performance or reliability.


Article ID: 124307 - Last Review: October 26, 2013 - Revision: 5.0
Applies to
  • Microsoft Windows NT Workstation 3.5
kbnosurvey kbarchive KB124307

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