Regarding the APM modes in the Toshiba HDD:
The "click" you hear after 5 minutes is the drive entering low power idle mode. The platter is still spinning at near full speed, but the heads are parked. That's the click you hear. The drive can recover from this mode very quickly since it only needs to unpark the heads, and relock the platter servo.
After an hour, the platter will slow down to about 40% speed. It's very difficult to hear the drive spin in this mode, but you still can if you listen carefully. Since the heads are already parked, this mode is sliently entered. The drive runs very cool in this mode, but spin-up is faster.
The equations are indeed confusing, but to engage both Y1 and Y2, you need to set Y1 first. If you only set Y2, Y1 will be set to the default value of 120 seconds. Either Y1 or Y2 are set depending on the range of the value being written. Writes between 80h-BFh (128d-191d) set Y1 and 01h-7Fh (1d-127d) set Y2. It requires two writes to set both.
So according to the datasheet,
Y1=(x-80h)*5+120 = (x-128d)*5+120 = (164-128)*5+120 = 300 sec
Y2=(x-40h)*60+600 = (x-64d)*60+600 = (114-64)*60+600 = 3600 sec
One final thing, make sure you don't call "hdparm -S". Also, I use the latest hdparm ipkg, not the one already installed on the router (note the full path to /opt/sbin/hdparm) though I don't think it's required.
- K.C.
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