Apple is now offering some interesting hard drive options for the 27" iMac.  It is not only possible to choose a SSD, but also to select both a SSD and hard drive at the same time.  To facilitate this, Apple has added a specific place for the SSD in the machine in a spot where there is a little free space.Unfortunately, as OWC outlined in its blog, if you do not select the optional SSD from the factory, your machine will not come equipped with the bracket and cables necessary for this disk.  This will make the subsequent installation of one of these drives very complex and perhaps impossible.

However, we have some excellent news for those of you who are worried about replacing a hard drive or who would like to put in a SSD in place of the original hard drive due to the specific temperature sensor for the original drive.

Simply put a jumper on the two pins on the motherboard to create a short circuit in order to deactivate the functionality.  Without doing this, the machine will start up in alarm mode and run the fans at full speed to try to cool the hard drive.  We expect that this procedure will also work with the 2009 machines.  We will try to confirm this as soon as we can.

With SSDs now available for practically every Mac, all that's left is to wait for Mac OS X to support TRIM!