The question is too vague; there are multiple types of power-saving modes for disks via ATA.
I can confirm that the X25-M, 320-series, and 510-series drives all offer http://www.sevenforums.com/tutorials/177819-ahci-link-power-management-enable-hipm-dipm.html DIPM capability as long as AHCI mode is in use (on Windows).
I can confirm that the X25-M, 320-series, and 510-series drives all provide Power Management as well as Interface Power Management capability. All drives advertise this capability via ATA specification standards (ATA_IDENTIFY (0xec) command). This means the drives support STANDBY and SLEEP modes.
I can confirm that the X25-M, 320-series, and 510-series drives do not provide http://en.wikipedia.org/wiki/Advanced_power_management# Device_power_states Advanced Power Management capability via ATA specification standards. This means the drives do not support APM. These drives do not advertise said capability, so the a proper operating system won't attempt to use it.
If you want hard proof/evidence of these statements I can provide it, but the output probably won't mean much to you since it will be mixed (some Windows screen shots, as well as some output from FreeBSD command-line).
