Apple Restricts Hard Drive Replacements on New iMacs
Apple has implemented a new temperature sensor system on its latest iMac models that will make it hard for users to replace their original hard drives in the case of failure or an upgrade. Without the new custom 7-pin hard drive cable and proprietary firmware included on stock hard drives. The new iMacs fans will spin to full speed and the machines will fail to pass the Apple Hardware Test. In the new 2011 machines the main 3.5" SATA hard drive bay has a new SATA power connector which is changed from a standard 4-pin power configuration to a 7-pin configuration. Hard drive temperature control is regulated by a combination of this cable and Apple proprietary firmware on the hard drive itself. Removing this drive from the system, or even from that bay itself, causes the machine's hard drive fans to spin at maximum speed and replacing the drive with any non-Apple original drive will result in the iMac failing the Apple Hardware Test (AHT). If you want to add a secondary drive either by installing it or using eSATA, that is still do able.
The change will affect anyone seeking to replace the hard drive in a new iMac they will have to go through Apple, limiting options and increasing costs.
Apple has never officially supported do-it-yourself hard drive replacements on the iMac for many years, but many users have still opted to take on the task themselves.