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A-4 Intel® Server RAID Controller U3-1 User’s Manual Rev 1.0
Hardware Details
Use Single-ended (SE) and Low Voltage Differential (LVD) devices but it is recommended that
you use only one type of drive (SE or LVD) on any one channel at a time. Each is explained below.
Note: If both an SE and LVD device are attached to the same channel the entire bus switches to single
ended mode. See Table A-4 for the maximum cable length distances that apply to each mode.
SRCU31 is an Ultra160 implementation and is backward compatable with older SCSI
specifications. See Table A-4 for the SCSI standards supported.
Single-ended (SE) Support
SRCU31 supports single-ended drives which operate at up to 40MB/sec depending upon the speed
of the drives attached.
Low Voltage Differential (LVD) Support
SRCU31 supports Ultra-2 LVD SCSI operating at up to 80MB/sec. and Ultra160 LVD SCSI
operating at up to 160MB/sec.
A.3.1.2. SCSI Connectors
SRCU31 includes an internal SCSI-3 Ultra Wide 68 pin connector and an external VHDCI (Very
High Density Connector Interface) 68 pin connector. Each connector can be fully populated with
up to 15 SCSI devices (not to exceed an additive total of 15 devices) as long as cable length
limitations for each segment are not exceeded.
Termination
This is a commonly overlooked requirement when connection SCSI devices together. When these
devices are connected together, the resulting set of devices is typically referred to as a SCSI bus.
SCSI devices such as hard disks and tape drives must be terminated if they are the last physical
devices at either end of the SCSI bus (if nothing else is actively terminating the end of the bus such
as a terminator or backplane). If a device is inserted into the middle of the SCSI bus, then it (the
device itself) should not be terminated. Only each end of the bus should be terminated.
Table A-4. SCSI Drive Standards for the Intel® Server RAID Controller U3-1
SCSI Drive Standard
Speed
MB/Sec
Bus Width
in Bits
Maximum Cable Length in
Meters
Intel® Server
RAID
Controller U3-
1 Maximum
Devices
Single-
Ended
LVD
SCSI-1 5 8 6 NA 8
Fast SCSI 10 8 3 NA 8
Fast Wide SCSI 20 16 3 NA 15
Ultra SCSI 20 8 1.5 NA 8
Ultra SCSI 20 8 3 NA 4
Wide Ultra SCSI 40 16 NA NA 15
Wide Ultra SCSI 40 16 1.5 NA 8
Wide Ultra SCSI 40 16 3 NA 4
Ultra2 SCSI 40 8 NA 12 8
Wide Ultra2 SCSI 80 16 NA 12 15
Ultra160 SCSI 160 16 NA 12 15