If the hdparm -I tells you that APM is at 254, then *it is* at 254
The value of 35 that you are talking about is another value that has nothing to do with it.
you refer to this line
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE
193 Load_Cycle_Count 0x0032 035 035 000 Old_age Always - 656598
The last column is the raw value, probably this is the absolute load cycle count, but who knows.
*If* the raw value is the absolute count, your disk had 656598 cycles
VALUE and WORST are normalized views of the raw value. If VALUE is reaching THRESH than the disk will die soon.
VALUE was probably 100 when the disk was new and was/is decreasing since then. If S.M.A.R.T. is right, you have 1 third of the load cycles left. Oh, but who says that it decreases linearly?
I did a search for your drive (I hope I got that right)
http://www.techhypermart.com/samsung-hm641ji-2-5-640gb-mobile-hard-disk-drive.html
says
- Load/Unload Cycles: 600,000
yours is at 656598, this could mean that its over the specificated load cycle counts yet.
Note that this does not correlate with the 1 third from above, sadly.
Another strange thing - your APM is at 254 according to the output from hdparm
It was mentioned that the APM level is not guaranteed to survive a reboot. Some OS's could set it at boot time, some will not.
It could be that a OS that does not make these clicking sounds is a OS that sets it at 254 at boot time. You will have to retrieve the value with the problem-os. Maybe you retrieved this value while the "good" OS was running, I do not know.
I encountered drives which APM was not changeable at all
Also note that the interpretation of the raw value is not standardized.
We are fishing in muddy waters without technical specifications from Samsung.