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What is SCSI “termination power”?

April 26, 2017SCSI

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What is SCSI “termination power”?

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At least one device (SCSI card or any SCSI drive) must provide power for the SCSI terminators by feeding 5 volts onto the TERMPWR line on the SCSI bus. Usually, termination power is fed through a diode to prevent backfeeding from a higher voltage source in case some other device is also supplying termination power. A good implementation will have a fuse to protect against shorts and a capacitor to cope with a sudden rise in termination power drain. The Apple SCSI cards do not provide termination power (though some recent Apple Hi-speed SCSI cards were modified by Apple to provide termination power). The RamFAST SCSI card can supply termination power. If a drive can supply termination power, I recommend letting it do so. The TERMPWR line can, in some cases, represent a significant load on the +5V rail going to the Slots. Both of my Quantum drive mechanisms provide termination power to the SCSI bus, avoiding the need to supply it from anywhere else. —————————- From: Rub