This does not apply to Serial ATA drives (SATA). SATA drives have one cable per drive.
ATA drives are configured at the factory for a cable select setting and is the recommend configuration on most computer setups. This allows the drive to assume the proper role of master or slave based on the connector used on the cable. For the cable select setting to work properly, the cables you are using must support the cable select feature. Current UltraATA cables with the 3 colored connectors do support this feature.
Setting master or slave is an alternate method to cable select. Depending on your computer and the existing hard drive, setting master/slave may be useful. One ATA (IDE) drive on the ribbon cable is referred to as a single drive. Two ATA drives physically plugged into the same 40-pin/80-conductor ribbon cable are paired in a master/slave set up. The drive jumpered as the boot drive is the C: or master drive. The drive jumpered as the non-boot drive is the slave drive. It is usually designated as the D: drive. Two ATA drives physically on two separate ribbon cables are not master/slave and are jumpered independently.
Determine which drive is the master and make sure it is jumpered correctly. Set the jumpers on the other drive to the slave setting. If one of your drives was made by another manufacturer, you will need to contact that manufacturer for master/slave jumper settings on that drive. The ATA ribbon cable has a marking along one edge. That marking or coloration marks pin 1. Make sure pin 1 on the ribbon cable is pointing towards pin 1 on both hard drives and also on the ATA controller card connector. Both hard drives will need a DC power connection.
Normally the newer drive will need to be the master. Different BIOSs and ATA controllers can impact this. If you have determined that both ATA drives are jumpered correctly for master/slave and they still do not work, try to bring the new drive up as a stand alone or single drive. If the new drive works fine as a stand alone and fails as a slave, try bringing it up as the master with the original drive as the slave. Jumper changes will be necessary on both drives.
If the drives work in this configuration, there is a decision to be made. You can leave the drives in the working configuration and transfer the necessary data from the original drive (now slave) to the new master drive. If the reverse configuration is preferred, then you will need to purchase a PCI Ultra ATA controller.
