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Termination Activate: The devices on the ends of the SCSI bus must terminate the bus for it to function properly. If the hard disk is at the end of the bus, setting this jumper will cause it to terminate the bus for proper operation. Not all drives support termination.
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Disable Auto Start: If present, this jumper will tell the drive not to automatically spin up when the power is applied, but instead wait for a start command over the SCSI bus. This is usually done to prevent excessive startup load on the power supply. Some manufacturers invert the sense of this jumper; they disable startup by default and provide an Enable Auto Start jumper.
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Delay Auto Start: This jumper tells the drive to start automatically, but wait a predefined number of seconds from when power is applied. It is also used to offset motor startup load on systems with many drives.
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Stagger Spin: When a system with many hard drives has this option set for each unit, the drives stagger their startup time by multiplying a user defined constant times their SCSI device ID. This ensures no two drives on the same SCSI channel will start up simultaneously.
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Narrow or Wide: Some drives have a jumper to control whether they will function in narrow or wide mode.
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Force SE: It allows Ultra2, Wide Ultra2, Ultra160, Ultra160+ or other LVD SCSI drives to be forced to use single-ended (SE) operation instead of LVD(low voltage differential).
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Disable Parity: Turns off parity checking on the SCSI bus, for compatibility with host adapters that do not support the features.
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This is not all of all. Many SCSI drives have some additional special features that are enabled through more jumpers. Some drives have replaced some of their jumpers with software commands sent over the SCSI interface.
