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The lower part of the enclosure has three drive bays for fixed-media mass storage devices. The enclosure includes data and power connectors for the boot drive and a second internal drive on the Ultra DMA/66 interface. It also has a power connector for a third internal drive.
The boot drive occupies one of the lower bays and is connected by way of an Ultra DMA/66 (ATA-5) interface. The Ultra DMA/66 cable assembly also has data and power connectors for a second 3.5 x 1-inch drive, which can be stacked on top of the boot drive.
The drives on the Ultra DMA/66 bus operate in a Device 0/1 configuration. The boot drive is device-select jumpered as Device 0 (master). Normally, an additional Ultra DMA/66 drive should be jumpered as Device 1 (slave). If necessary, the device configurations of the drives could be reversed, but in any case, the two drives on the Ultra DMA/66 bus must be configured complementarily.
The Ultra DMA/66 bus supports PIO Mode 4, DMA Mode 2, and Ultra DMA Mode 2 data transfers.
The other two lower bays are available for devices connected to a separate PCI controller card. An Ultra SCSI 160 drive and Ultra SCSI 160 PCI controller card are available as a configuration option.
None of the lower drive bays can be modified to support removable-media drives.
The boot disk in the Power Mac G4 computer is installed in one of the lower bays and connected by way of the Ultra DMA/66 (ATA-5) interface.
An Ultra SCSI 160 drive and Ultra SCSI 160 PCI controller card are available as a configuration option. The Ultra SCSI 160 is a low-voltage differential (LVD) interface and provides data transfer rates of up to 160 MB per second. For additional information about Ultra SCSI, refer to the reference shown in Ultra SCSI Interface.