If you read the article a little more carefully, you'll understand that it's still the same SATA 15-pin connector (I mean if it wasn't, you would have seen arti

If you read the article a little more carefully, you'll understand that it's still the same SATA 15-pin connector (I mean if it wasn't, you would have seen articles about how you couldn't swap hard drives at all). But what OWC is claiming is that now, instead of using pins 4,5,6 and 12 for ground - that the new iMacs and harddrives inside them are using some of those pins for communication, specifically temperature sensor. This is outside of the SMART specification, which passes information about the harddrive over the data cable (not the power cable). So you can swap in any harddrive you like - but if your harddrive doesn't have the functionality / firmware in it to communicate temperature information over the power cable, then the fans kick in. At this point, I'm offhandedly wondering if this is related more to the Intel Z68 chipset / Smart Response technology somehow. In addition, OWC is claiming that there's "Mac specific" firmware because they swapped out an identical model harddrive and ran into an issue - but (playing devil's advocate), if these are new temperature sensors involved, a firmware upgrade wouldn't cut it - the harddrive would still be missing said sensors. I would believe OWC more if they swapped the boards on the harddrives while leaving the platter casing intact.