HP Vectra Technical Reference Manual page 248

SECTION 8. DISC
This section discusses the ROM BIOS disc drivers. The disc driver (INT 13H) provides a set of
functions that control the disc drives and data transfer between the disc drives and the system.
8.1 Overview
The disc driver supports three disc types; standard capacity flexible discs (360KB), high capacity
flexible discs (1.2 MB), and hard discs. The structure of the disc driver allows additional drives to
be easily integrated into the system.
The disc driver consists of two separate code modules; a module that supports flexible disc
drives, and one that supports hard disc drives. The code module that provides the flexible disc
support is contained in the ROM BIOS that resides on the Processor Extension Card. The code
module for the hard disc drive is resident in a ROM on the hard disc adapter card.
8.1.1 Physical Drive Numbers
Each drive in the system has a physical drive number. Physical drive numbers for flexible discs
start with 0, while physical drive numbers for the hard disc start with 80H. In a typical system
configured with one high capacity flexible disc drive, one standard capacity flexible disc drive,
and one 20MB hard disc drive, the physical drive numbers would be 0, 1, and 80H respectively.
Flexible disc drives have a one-to-one correspondence between physical drives and volumes.
However, hard disc drives may have more than one volume, and
consequent~y
more than one
physical drive number. The optional 40MB hard disc drive can be configured as two 20MB
volumes.
A
40MB hard disc will have two physical drive numbers assigned to it (80H and 81 H).
Physical voluming of disc drives is not the same as operating system partitions, and the two
should not be confused. See the Vectra MS-DOS Programmer's Reference Manual for more
information on disc partitions.
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