Pata Device Classes - HP Compaq dx6100 MT Reference Manual

Each drive attached to a channel must have a drive designation. If a drive is attached to the
Device 0 cable position and its cable-select jumper is present, the drive is designated as Device
0. Similarly, if a drive is attached to the Device 1 cable position and its cable-select jumper is
present, the drive is designated as Device 1.
For optimal performance of a computer system, all drives need to be attached to the PATA
channel(s) in a specified sequence. This sequence is determined by the device class of the drives
and by specific attach sequence rules.

4.3.1 PATA Device Classes

In order to determine the best drive attach sequence, ATA/ATAPI drives are segregated into four
different classes based upon the bandwidth demands they place on an ATA channel. The most
demanding devices are in Class 1 and the least demanding are in Class 4.
Class 1
Hard
Drives
ATA-100
ATA-66
ATA-33
General Attach Guidelines
■
The lower the device class number, the faster the device and the more bandwidth required.
■
Drives installed in the Device 0 positions on both the primary and secondary channels
receive the greatest possible bandwidth.
■
The bootable ATA hard drive should always be installed on the primary channel in the
Device 0 position.
Service Reference Guide, dx6100
Class 2
High Speed
Optical Drives
DVD
DVD-CD R/W
361293-003
Serial and Parallel ATA Drive Guidelines and Features
Class 3
Optical Storage
Drives
R/W CD-ROM
CD-ROM
Class 4
Magnetic
Storage Drives
LS-120
Tape
Zip
4–5