Explanation of X86 Boot Drive Limitations

 Last reviewed: March 26, 1997
Article ID: Q154052
The information in this article applies to:
  • Microsoft Windows NT Workstation versions 3.5, 3.51 and 4.0
  • Microsoft Windows NT Server versions 3.5, 3.51 and 4.0

SUMMARY

During Setup, Windows NT can only be installed within the first 1,024 cylinders of the boot drive. This is due to Interrupt 13 limitations on x86 computers.

MORE INFORMATION

When starting an x86 based computer, Ntdetect.com retrieves and stores Interrupt 13 information. This information is supplied by the computer's BIOS. Only information for the first two disks in the system is saved. This information about the drive layout is then passed to the operating system during initialization. The amount of space that the operating system files can use to boot the system is limited in Windows NT to the first 1,024 cylinders of disk 0. This means that Ntldr, Boot.ini, Ntdetect.com and the Windows NT operating system files must be within this boundary.

If the disk controller is using a 32 sector/64 head translation scheme, this boundary will be 1 GB. If the controller uses 63 sector/255 head translation, the limit will be 4 GB. If there is a secondary controller that does not have BIOS enabled, Windows NT will default to 32 sectors/64 heads. In some cases, such as duplexing, this may cause identical drives on different controllers to be interpreted as being slightly different in size.

Additional query words: prodnt
Keywords : kbsetup ntfilesys ntsetup NTSrvWkst
Version : 3.5 3.51 4.0
Platform : WinNT

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Last reviewed: March 26, 1997
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