Intel SRCU31 Scsi Connectors, Single-ended SE Support, Low Voltage Differential LVD Support

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-4for 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-4for 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.

Table A-4. SCSI Drive Standards for the Intel®			Server RAID Controller U3-1
				Maximum Cable Length in			Intel® Server
	SCSI Drive Standard	Speed	Bus Width		Meters		RAID
							Controller U3-
		MB/Sec	in Bits
				Single-			1 Maximum
						LVD
				Ended			Devices
	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

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.

A-4 Intel® Server RAID Controller U3-1 User’s Manual Rev 1.0