Standard hard drives, without Apple’s custom firmware, don’t provide temperature monitoring in the way that the new iMacs require:
For the main 3.5″ SATA hard drive bay in the new 2011 [iMacs], Apple has altered the SATA power connector itself […]. Hard drive temperature control is regulated by a combination of this cable and Apple proprietary firmware on the hard drive itself. From our testing, we’ve found that 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).
In examining the 2011 27″ iMac’s viability for our Turnkey Upgrade Service, every workaround we’ve tried thus far to allow us to upgrade the main bay factory hard drive still resulted in spinning fans and an Apple Hardware Test failure. We swapped the main drive out (in this case a Western Digital Black WD1001FALS) with the exact same model drive from our inventory which resulted in a failure. We’ve installed our Mercury Pro 6G SSD in that bay, it too results in ludicrous speed engaged fans and an AHT failure. In short, the Apple-branded main hard drive cannot be moved, removed or replaced.
(Then the piece turns into a weak political argument that’s probably better suited somewhere else.)
I don’t think this is a big deal: iMac hard drives are not considered user-serviceable at all, since accessing the bay requires the extremely risky removal of the screen (and the dust-free reattachment afterward). This is something that Apple only wants authorized service centers to do, understandably, because otherwise they’d have a bunch of people botching the repair and then complaining to unfortuate Genius Bar workers that their now-much-more-broken iMac should be replaced at Apple’s expense.
Since Apple doesn’t need to support non-Apple-branded hard drives in this machine, they can take shortcuts to slim down the design, improve reliability, reduce parts, and reduce cost. And it looks like one of those shortcuts is that they no longer need a separate cable and sensor to monitor the hard drive’s temperature — they can now read the drive’s internal sensor directly through the SATA power cable’s unused pins, as long as the drive has their custom firmware to send the data to those pins.
The iMac is a very clear, known tradeoff to the types of geeks like us who would even think about replacing its internal hard drive ourselves (or having an unauthorized place do it to save money or add unsupported parts):
You get a beautiful, slim, all-in-one, high-end Mac, with one of the best LCD panels on the market built in, for a very good price relative to PCs and an excellent price relative to the other Macs. For these benefits, you give up all after-purchase internal customization, expansion, and self-repairs, except RAM. If you want a more customizable desktop, you can either get a Windows PC (which, if you want a Mac, isn’t an alternative), you can spend a lot more money for a Mac Pro, or you can just deal with the iMac’s limitations.
Michael from OWC is upset1 because they can’t continue to offer one part of a service that Apple has never permitted, on a non-user-serviceable part, to install unsupported hardware — and that this is the result of Apple being unnecessarily evil, rather than the more pragmatic explanations. It doesn’t seem like a very strong argument.
He’s also predisposed to discredit the new iMacs because he recently bought the prior version and wants to assure himself that he made the right purchase. ↩