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 connected to an optional PCI controller card.
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 4 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.