Hardware Reference
In-Depth Information
• Master (dual drive)
• Slave (dual drive)
• Cable select
Most drives simplify this to three settings: master, slave, and cable select. Because each ATA drive
has its own controller, you must specifically tell one drive to be the master and the other to be the
slave. No functional difference exists between the two, except that the drive that's specified as the
slave asserts a signal called DASP after a system reset informs the master that a slave drive is
present in the system. The master drive then pays attention to the drive select line, which it otherwise
ignores. Telling a drive that it's the slave also usually causes it to delay its spin-up for several
seconds to allow the master to get going and thus to lessen the load on the system's power supply.
Until the ATA specification, no common implementation for drive configuration was in use. Some
drive companies even used different master/slave methods for different models of drives. Because of
these incompatibilities, some drives work together only in a specific master/slave or slave/master
order. This situation mostly affects older IDE drives introduced before the ATA specification.
Most drives that fully follow the ATA specification now need only one jumper (master/slave) for
configuration. A few also need a slave present jumper.
Table 7.5
shows the jumper settings that most
ATA drives require.
Table 7.5. Jumper Settings for Most ATA-Compatible Drives on Standard (Non-Cable Select)
Cables
Note
If a cable select cable is used, the CS jumper should be set to On and all others should be set to
Off. The cable connector then determines which drive will be master or slave.
Figure 7.7
shows the jumpers on a typical ATA drive.
