Windows NT can take advantage of hard disks with more than 1024 cylinders if you enable extended translation. Windows NT does not have a limit to the number of cylinders it can address, but the system and boot partitions are limited to 1024 cylinders by the system BIOS, which must use INT 13 to access the disk during startup. The section "Starting and Ending Head, Sector, and Cylinder Fields," presented earlier in this chapter, contains more information about the system and boot partitions.
The following error messages might appear when extended translation is not enabled on disks larger than 1024 cylinders, and the Master Boot Record is unable to locate the Partition Boot Sector:
If you create your system and boot partitions in Windows NT Setup, you do not have to concern yourself with these details, because Setup will not create a partition that cannot be used to start Windows NT.
When Windows NT has completed startup, it does not use the values in the Starting and Ending Head, Sector, and Cylinder fields of the Partition Table. Instead, it uses the Relative Sectors and Number Of Sectors fields. These fields provide a full 32 bits to represent sectors, which results in volumes of up to 232 sectors.
With a standard sector size of 512 bytes, the 32-bit fields used for the Relative Sectors and Number of Sectors result in a maximum possible volume size of:
512 bytes x 4,294,967,296 = 2,199,023,255,552 bytes, or 2 TB.
When creating partitions or logical drives on a disk, Windows NT writes the correct values to the Partition Table fields whenever possible. When the Ending Cylinder field for an entry in the Partition Table goes beyond cylinder 1023, Windows NT writes the maximum permitted values to these fields in the Partition Table. This prevents the system BIOS from calculating the Starting and Ending addresses based on erroneous data.
There are several Knowledge Base articles that discuss using large disks. Knowledge Base articles are included on the Windows NT Workstation Resource Kit CD.