PC Hardware in a Nutshell, 3rd Edition

Master/Slave guidelines

When deciding how to allocate devices between two interfaces and choose Master versus Slave status for each, use the following guidelines:

• Always assign the main hard drive as Primary Master. Particularly if your hard drive supports fast DMA modes (ATA-66 or ATA-100), do not connect another device to the primary ATA interface unless both positions on the secondary interface are occupied.

• ATA forbids simultaneous I/O on an interface, which means that only one device can be active at a time. If one device is reading or writing, the other device cannot read or write until the active device yields the channel. The implication of this is that if you have two devices that need to perform simultaneous I/O—e.g., a CD writer that you use to duplicate CDs from a CD-ROM drive—you should place those two devices on separate interfaces.

• If you are connecting an ATA device (a hard drive) and an ATAPI device (e.g., an optical drive or a tape drive) to the same interface, set the hard drive as Master and the ATAPI device as Slave.

• If you are connecting two similar devices (ATA or ATAPI) to an interface, it generally doesn’t matter which device is Master and which Slave. There are exceptions to this, however, particularly with ATAPI devices, some of which really want to be Master (or Slave) depending on which other ATAPI device is connected to the channel.

• If you are connecting an older device and a newer device to the same ATA interface, it’s generally better to configure the ...