Appendix C SCSI Devices

Media Tray Target IDs

The default SCSI ID numbers for devices in the media tray are:

Table C-1 Media Tray Default SCSI ID Numbers

Device	ID
CD-ROM	6
Tape drive	5

Disk Board Target IDs

Default SCSI ID Numbers

The default SCSI ID numbers for disk drives on the Disk boards are listed by server type in TABLE C-2.

Table C-2 Disk Board Default SCSI Disk Drive ID Numbers

	Board Slot	Disk 0,1	Board Slot	Disk 0,1
Enterprise 4500 or 5500
	0	4, 5	1	6, 7
	2	0, 1	3	10, 11
	4	2, 3	5	12, 13
	6	8, 9	7	14, 15
Enterprise 6500 only
	14*	0, 1	15*	10, 11
*Enterprise 6500 systems: Disk boards can only be installed in slots 14 and 15.

Overriding A Default Disk Board Target ID

You can override the default IDs by jumpers on each disk board. Each disk has an ID_ENABLE jumper and four ID jumpers. If the ID_ENABLE jumper is not installed, the disk drive uses the default SCSI ID. If the ID_ENABLE jumper is installed, the disk drive uses the ID specified by the four ID jumpers located on the disk board (an installed jumper indicates a logical 1).

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Note -

For Enterprise 4500 and 5500 servers, default disk drive ID numbers are chosen so that IDs 4, 5, 6, and 7 are unlikely to be assigned to disk drives. These IDs are in slots 0 and 1, which are normally taken by a CPU/Memory+ board (slot 0) and an I/O board (slot 1).

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SCSI Cable Length

The maximum combined length for a string of SCSI cables is 6 meters for non-differential cables. For differential SCSI cables, the maximum is 25 meters. To calculate the total length of a SCSI string, include external cables, internal cables, and printed traces. Table C-3 lists measurements for Enterprise servers.

Table C-3 Internal SCSI Lengths (Approximate)

Location	Internal Length	Comments
Enterprise 6500 slot 1	3.7 meters	Includes I/O+ board traces and cables to media tray
Enterprise 5500 slot 1	3.7 meters	Includes I/O+ board traces and cables to media tray
Enterprise 4500 slot 1	1.4 meters	Includes I/O+ board traces and cables to media tray
SBus+ I/O board	0.43 meter	Includes board traces only
Graphics+ I/O board	0.43 meter	Includes board traces only
Disk board	0.64 meter	Includes board traces only

SCSI Termination

The I/O+ board in slot 1 of any Enterprise server must be terminated. This slot connects to the media tray through cables and a connector on the centerplane.

I/O+ boards in other slots do not require termination if no devices connect to the SCSI bus on those boards.