Drive installation guidelines
Most workstation system boards have two ATA (IDE) controller channels with a dedicated connector for
each controller. One controller is designated as the primary and the other as the secondary controller.
Each of the two controllers can have up to two devices attached to it. Each workstation system might
therefore have a maximum of four ATA/ATAPI drives. All drives are connected to these controllers using
an industry-standard, 80-conductor cable.
included as a part of the maximum four drives.
Any drive attached to a controller must have a drive designation. If only a single drive is connected to
a controller and its jumper is in the cable-select position, it is designated as the Master Drive (Drive/
Device 0) by its attachment to the Drive/Device 0 cable position. If two cable-selected drives are
connected to a single controller, one will be designated by its attachment to the cable as the Master
(Drive/Device 0) and the other as Slave (Drive/Device 1).
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.
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.
Class 1 Hard
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
Attach sequence rules by class priority
Drives should be attached in the sequence shown for optimum performance starting at position 1.
Appendix C Appendix C — Ultra ATA devices
The industry standard, 1.44-MB diskette drive has its own separate channel and is not
Class 2 High Speed
Class 3 Optical storage
Class 4 Magnetic