That clicking comes from the drive's internal power management. The correct name is Advanced Power Management. You set it via ATA feature register 0x05. Register 0x85 means disable, but is optional, thus the 254 thing with hdparm. Disabling SMART won't make it stop.
I don't know about ata, but in sata, there definitely seems to be no code which actually controls a drive's internal power management, controlled by these feature registers. It does do acoustic management (also controlled by a feature register) by proxying it with a vendor specific SCSI mode page, that's about it. This issue is bugging me too and preventing me from putting OpenSolaris on my laptop. -mg This message posted from opensolaris.org
