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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:
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:
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.
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