DOCUMENT ID: 1258-02 SYNOPSIS: How does fdisk obtain physical geometry parameters OS RELEASE: 2.1, 2.4 PRODUCT: Solaris KEYWORDS: fdisk physical geometry parameters disk drive DESCRIPTION: Describes the procedures used by fdisk to obtain the geometry parameters display when using the "fdisk -G" command. SOLUTION: Two types of disk drives technologies are most common: wd1003 and SCSI. The wd1003 types include IDE, MFM, RLL, and ESDI. These drives usually use CMOS entries to announce availability to the system. The wd1003 terminology is a result of its being the first controller used by IBM in the AT series. SCSI disks don't have any indication in CMOS. The controller BIOS will announce availability to the system. Some controllers will emulate geometry's for DOS compatibility. SCSI technology specifies disk drives to have physical parameters written on them as part of the manufacturing process. Fdisk issues an ioctl command to the disk driver using DKIOCG_PHYGEOM parameter. The geometry of the disk indicated by the ioctl reference will be returned. Two different sources are used to obtain actual parameters: wd1003 (CMOS) and SCSI (the actual disk drive). SCSI has a command "Get size" to ask the drive for parameters. SCSI controller emulation may return other than actual parameters. DATE APPROVED: 02/15/95