Device Classes; General Attach Guidelines; Attach Sequence Rules By Class Priority - HP Xw8400 - Workstation - 4 GB RAM Technical Reference Manual

For optimal performance of a workstation system, all drives must be attached to the ATA controllers in
a specified sequence. This sequence is determined by the device class of the drives and by specific
attach sequence rules.

Device classes

To determine the best drive attach sequence, ATA/ATAPI drives are segregated into four different
classes based on the bandwidth demands they place on an ATA controller. The most demanding devices
are in Class 1 and the least demanding are in Class 4.
Table C-1 Device classes
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 controllers receive
the greatest possible bandwidth.
●
The bootable ATA hard drive should always be installed on the primary controller in the Device 0
position.

Attach sequence rules by class priority

Drives should be attached in the sequence shown for optimum performance starting at position 1.
Installing drive order
*If there are three or more devices, two or more of which are hard drives, two hard drives should be
attached to the primary controller first before following the general attach sequence rule.
The attach sequence rule can also be stated in table format:
Table C-2 General attach sequence rule
Sequence
1
2
144 Appendix C Appendix C — Ultra ATA devices
Class 2 High Speed Class 3 Optical storage
optical drives drives
DVD R/W CD-ROM
DVD-CD R/W CD-ROM
The lowest class drive—Bootable hard drive recommended.
If only two drives, the last drive goes here; otherwise, the lowest class of the remaining drives goes
here.
Class 4 Magnetic
storage drives
LS-120
Tape
Zip
Description
ENWW