Description 11
SCSI Controller
The SCSI version of the server board includes an embedded Adaptec† AIC-7899W controller
providing dual Ultra160 Low Voltage Differential (LVD) SCSI channels.
The SCSI bus is terminated on the server board with active terminators that cannot be disabled.
The onboard device must always be at one end of the bus. The device at the other end of the cable
must also be terminated. LVD devices generally do not have termination built-in and need to have
a termination source provided. Non-LVDs devices generally are terminated through a jumper or
resistor pack on the device itself.
ATA-100 Controller
The ATA version of the server board provides an embedded dual channel ATA-100 bus through the
use of the Promise Technology† PDC20277 ATA-100 controller. The controller contains two
independent ATA-100 channels that share a single 32-bit, 33-MHz PCI bus master interface as a
multifunction device. The controller supports:
• DMA and PIO IDE drives and ATAPI devices
• ATA and ATAPI proposal PIO Mode 0, 1, 2, 3, 4; DMA Mode 0, 1, 2; and Ultra DMA Mode
0, 1, 2, 3, 4, 5
• IDE transfer rates up to 100 MB/sec per channel
• Host interface complies with PCI Local Bus Specification Revision 2.2

IDE RAID

The ATA-100 controller supports IDE RAID through both ATA-100 channels. In a RAID
configuration, multiple IDE hard drives are placed into one or more arrays of disks. Each array is
seen as an independent disk, though the array may include one, two, three, or four drives. The IDE
RAID can be configured as follows:
• RAID 0: Striping one to four drives
�� RAID 1: Mirroring two drives
• RAID 1 +: Spare drive (three drives)
• RAID 0 +: One to four drives are required
RAID 0 configurations are used for high performance applications, as it doubles the sustained
transfer rate of its drives. RAID 1 configurations are primarily used for data protection. It creates
an identical drive backup to a secondary drive. Whenever a disk write is performed, the controller
sends data simultaneously to a second drive located on a different data channel. With 4 drives
attached to dual ATA-100 channels, two striped drive pairs can mirror each other (RAID 0+1) for
storage capacity and data redundancy.