multi(W)disk(X)rdisk(Y)partition(Z)

This form of the ARC pathname is only used on x86-based computers. On Windows NT version 3.1, it was only valid for IDE, EIDE, and ESDI disks. In Windows NT 3.5 and later, it is valid for SCSI disks as well.

The multi() syntax indicates to Windows NT that it should rely on the system BIOS to load system files. This means that NTLDR, the boot loader for x86-based computers, will be using interrupt (INT) 13 BIOS calls to find and load Ntoskrnl.exe and any other files it needs to get the system running.

Note

The term multi() syntax refers to the multi(W)disk(X)rdisk(Y)partition(Z) form of the ARC pathname.

The W, X, Y, and Z parameters have the following meaning:

• W is the ordinal number of the controller, and should always be 0.
• X is not used for multi(), and is always 0.
• Y is the ordinal for the disk on the controller, and is always 0 or 1 for disks connected to the primary controller. The range is 0 through 3 for disks on a dual-channel EIDE controller.
• Z is the partition number. All partitions receive a number except for type 5 (Extended) and type 0 (unused) partitions. These numbers start at 1, as opposed to all other entries, which start with 0.

Theoretically, the multi() syntax could be used to start Windows NT from any disk on the computer. However, this would require that all disks be correctly identified through the standard INT 13 interface. But support for this varies from controller to controller, and most system BIOS only identify a single controller through INT 13.

For a configuration with IDE or EIDE disks, the multi() syntax works for up to four disks on the primary and secondary channels of a dual-channel controller. In a SCSI-only configuration, the multi() syntax works for the first two disks on the first SCSI controller (the controller whose BIOS loads first). When your computer has both SCSI and IDE or EIDE disks, the multi() syntax works only for the IDE or EIDE disks on the first controller.