Device Classes; Attach Sequence Rules By Class Priority; Additional Drive Application Notes - HP xw4200 Service And Technical Reference Manual

Device Classes

To determine the best drive attach sequence, Ultra ATA/ATAPI drives are segregated into four different
classes based on the bandwidth demands they place on an Ultra ATA controller. The most demanding
devices are in Class 1. The least demanding devices are in Class 4. The following table illustrates those
classes.
Table C-1
Device Classes
Class 1 Class 2
Hard Drives High Speed Optical Drives
Ultra ATA-100 DVD
Ultra ATA-66 DVD-CD R/W
Ultra 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 position receive the greatest possible bandwidth.

Attach Sequence Rules by Class Priority

The following table summarizes the attach sequence rule.
Table C-2
General Attach Sequence Rule*
Sequence Description
1 The lowest class drive—bootable hard drive recommended.
2 If only two drives, the last drive goes here; otherwise the lowest class of the remaining drives.
*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.

Additional Drive Application Notes

When replacing a hard drive, the replacement should be of the same type (Ultra ATA 33, -66, or
-100) as that being removed to retain the same level of performance.
When Ultra ATA and SATA hard drives are mixed in the same system, the SATA drive will become the
boot drive unless the boot order is changed in Computer Setup (F10). The default boot order on this
system prefers SATA, then Ultra ATA, then SCSI.
Class 3 Class 4
Optical Storage Drives Magnetic Storage Drives
R/W CD-ROM LS-120
CD-ROM Tape
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DRIVE INSTALLATION GUIDELINES 161