Why can I only see 127 to 137 GBytes of my 160+ GB drive in Windows NT v4?
Windows NT v4 on a Traditional Motherboard
Microsoft Windows NT v4 SP4 or higher has a native limitation of 137GB supporting ATA interface disc drives that are attached to traditional Primary and Secondary IDE Channels on the motherboard. In this configuration WinNT4 will not create partitions greater than 137GB.
Since the likelihood that an existing Windows NT installation will be on an older BIOS and motherboard is high, it is best to use a controller card when adding an ATA drive greater than 137GB. The sensitivity of the operating system to changes can create difficult recovery scenarios and the controller card approach, which is based on a SCSI-type of support model, is significantly easier.
If your system's old boot drive is less than 137GB and uses a drive overlay program (DDO) to overcome a previous BIOS capacity limitation (such as Disk Manager or previous versions of DiscWizard or MaxBlast, and identifiable as a blue banner box before the operating system loads), then the Intel Application Accelerator is incompatible with your system. If you have this legacy configuration, the Ultra ATA controller card is the only solution for Windows NT. If you install the Intel Application Accelerator (IAA) on this type of system, loss of data will occur. If you are not sure if your system uses a DDO, contact Seagate Support.
Some sources may suggest the IAA. While it is true that Windows NT is listed, for the purposes of this discussion, Seagate only suggests the IAA as an alternative when building a new system and not for adding a drive to an existing Windows NT system.
Windows NT supports FAT16 and NTFS file systems. Several partitioning rules exist for Windows NT which are beyond the scope of this paper. For further information, see the following Microsoft articles:
Q114841 - "Windows NT Boot Process and Hard Disk Constraints"
Q119497 - "Boot Partition Created During Setup Limited to 4 Gigabytes"
Q138364 - "Windows NT Partitioning Rules During Setup"
New System Considerations
Boot partitions are limited to 4GB. The size of the boot partition generated by Windows NT setup is limited to 4 gigabytes (GB) because Windows NT Setup must first format the partition to the FAT file system. Although it is possible to select NTFS for the boot partition during Setup, this partition is first formatted to FAT, Setup completes, then the partition is converted to NTFS. Because the FAT file system is limited to a 4-GB partition size, the boot partition for Windows NT is also effectively limited to 4 GB (119497 - "Boot Partition Created During Setup Limited to 4 Gigabytes").
The remaining capacity of the drive can be prepared as an NTFS partition from within the Windows environment after loading the operating system.
Formatting a drive past the 137GB barrier on a system that does not meet all requirements of BIOS support and the Intel Application Accelerator 48-bit Addressing operating system drivers will result in data loss. Seagate is not responsible for lost data.
If you have an Intel compatible chipset, and after the OS and IAA are installed, any additional gigabytes will show up later as unallocated space on the drive. You can easily create a second partition with the Windows Disk Management partitioning tool.
Windows NT v4 on a PCI Controller Card
Controller cards support ATA interface disc drives through their own onboard BIOS and Windows device drivers. Since the drives are supported by drivers that emulate the SCSI driver approach, the native Windows 137GB ATA limitation does not apply since those drivers are not in use.
If your disc drives are recognized by the controller BIOS when the system is first powered on but later the drives are not seen by Windows then the device drivers for the controller card need to be installed. See your controller card documentation for direction.
Please see our list of PCI vendors which are known to manufacture ATA controller cards that support drives greater than 137GB.
Windows NT supports FAT16 and NTFS file systems. Several partitioning rules exist for Windows NT which are beyond the scope of this paper. For further information, see the following Microsoft articles:
Q114841 - "Windows NT Boot Process and Hard Disk Constraints"
Q119497 - "Boot Partition Created During Setup Limited to 4 Gigabytes"
Q138364 - "Windows NT Partitioning Rules During Setup"
New System Considerations
When building a new system, if you are using a ATA/133 PCI controller card which includes new ATA or ATAPI disk device drivers, the Windows NT operating system installation will pause briefly and ask for you to insert a OEM floppy diskette. This pause for new "SCSI or RAID adapter" drivers happens soon after the boot near the beginning of the installation. See your controller documentation for specifics.
Adding a Drive to an Existing System
The installation procedure is relatively easy if your original boot drive is attached to the motherboard and your new drive is attached to the controller card as additional storage. If you want your new drive to become the boot drive, your system BIOS must have an option to control the boot device or to release boot control from the Primary Master to the controller card. This is sometimes listed as "boot from SCSI".
For more background information about 48-bit LBA addressing please visit our overview on this issue. You may also use our Capacity Limitations Walk-Through for 137 GByte limits, as well as other capacity limitations.
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