The power-on timer (Attribute 9 raw value) on my Maxtor disk acts strange.
There are three related problems with Maxtor's SMART firmware:
1. On some Maxtor disks, the raw value of Attribute 9 (Power On Time) is supposed to be minutes. But it advances at an unpredictable rate, always more slowly than one count per minute. This is because when the disk is in idle mode, the counter stops advancing. This is only supposed to happen in standby mode. This will be corrected in Maxtor product lines released after October 2004.
2. In Maxtor disks that use the raw value of Attribute 9 as a minutes counter, only two bytes (of the six available) are used to store the raw value. So it resets to zero once every 65536=2^16 minutes, or about once every 1092 hours. This is fixed in all Maxtor disks manufactured after July 2003, where the raw value was extended to four bytes.
3. In Maxtor disks that use the raw value of Attribute 9 as a minutes counter, the hour time-stamps in the self-test and ATA error logs are calculated by right shifting 6 bits. This is equivalent to dividing by 64 rather than by 60. As a result, the hour time stamps in these logs advance 7% more slowly than they should. Thus, if you do self-tests once per week at the same time, instead of the time-stamps being 168 hours apart, they are 157 hours apart. This is also fixed in all Maxtor disks manufactured after July 2003.