Sometimes even the best educated guesses can be thrown for a loop when an unforeseen “X-Factor” comes into play. Such is the case with the Late 2009 iMacs.
As we were getting information together for the new iMac instructional videos, we came across a little tidbit that, apparently, hasn’t been covered anywhere else: Apple has switched the iMac’s method of hard drive temperature sensing. They’ve gone from an external sensor that attached to the outside surface of the drive to a connector that seems to use the drive’s internal sensors.
On first blush, this would appear to be a good thing; an internal sensor is closer to the drive’s mechanics and is likely to be more accurate regarding drive state. Unfortunately, there are no industry standards regarding the ports/pins used to access this information, and each hard drive manufacturer seems to do it their own way. And more unfortunately, when the iMac gets no sensor information via that cable, the heat exhaust fans kick into permanent high gear, so that cable must be connected.
That means, in order to upgrade the internal drive, you need to have a connector cable that’s compatible with the brand of drive that you’re installing… and that’s an Apple service part not generally available to the end user. Pretty sneaky, Apple!
Fortunately, you can reuse the cable that came with your iMac as long as you replace the drive with another model from the same manufacturer we have confirmed works properly with this thermal sensor cable. To determine what brand hard drive your iMac has, go to About This Mac, click on Serial-ATA, and then look for the drive model installed at the factory. If the model has the preface WD, that’s a Western Digital hard drive and if your drive has a ST, that’s a Seagate hard drive. Once you know what drive came with your Mac, you can upgrade to a larger drive and continue to use the thermal sensor…thus avoiding the “ear pleasing” whoosh of fans on high.
Here’s a list of the drives that install into WD factory equipped iMacs:
- 1.0TB Western Digital Caviar Black
- 1.0TB Western Digital Caviar Green
- 1.5TB Western Digital Caviar Green
- 2.0TB Western Digital Caviar Green
For the Seagate equipped models, these drives from us will plug right into the thermal cable:
Fortunately, upgrading memory is still easy to do, and will show a more immediate improvement in performance than will a hard drive upgrade. That doesn’t mean, though, that somewhere down the road you won’t want to upgrade your hard drive to something larger and/or faster.
We’re all about giving you the most options for upgrading your Mac and that’s why OWC is looking into potential ways to turn this curveball from Apple into a Home Run for you. As soon as we can find a viable method for connecting a different brand hard drive than the one that came with your 2009 iMac, you can be sure you’ll hear it first right here on the OWC Blog.
In the meantime, if you get stuck for storage, you can always take advantage of that lone FireWire 800 port (or, if necessary, one of those USB 2.0 ports) and add a fast external storage device, such as the Mercury Elite-AL Pro. The benefit of this is that when you are able to upgrade that internal drive to your preference, you will have a handy extra external unit for backing up to.
Keep tuned to the OWC Blog for updates…
Monday, 16. November 2009
I picked up a 27″ iMac when they came out and immediately cracked it open to replace the 1TB HDD with an OCZ Vertex SSD drive. I came across this ‘proprietary’ connector but although it connects to the motherboard labelled ‘HDD Temp’, it looks to me like the HDD is just a standard Western Digital HDD and it’s connected across the two jumpers which slow the drive to SATA-150 (according to the technical information available from WD’s website).
I did notice that when the cable isn’t connected the fans spin up to maximum speed, if you simply use a piece of wire in a ‘U’ shape to essentially join the two wires of the connector together, the fans operate at around 1100RPM which is fine for the SSD drive.
I don’t think the HDDs that Apple are using are anything special, and if that’s the case then this connector is simply sensing the presence of a HDD rather than reading temperature information from it. Just my own thoughts.
My SSD installation is 100% and the drive works perfectly. The HDD fans stay around 1100RPM with the little wire trick, which is more than enough for my purposes.
Monday, 16. November 2009
Hi Nathan and thanks for stopping by. We suggest using caution in not using the cable correctly. It is designed to provide thermal zone monitoring so basically if your HD overheats, you’re not turning the fan on in that zone to cool it down. Realize you’re using an SSD…but still…
Thursday, 19. November 2009
I have a new 27″ iMac with a Seagate 1T drive. Seagate has a 4 pin jumper block that the thermal sensor connects to. Seagate shows that jumper block as the SATA 150 / SATA 300 jumper, very strange. Of course I bought a 2T WD green drive to replace the 1T drive. HD fan spins full speed without the sensor cable.
Thursday, 19. November 2009
Judging by the documentation that I was able to find on the drive, only two of those pins in the jumper block refer to the 150/300 switching. The other two pins (which the Apple jumper connector attaches to) would appear to connect to an internal sensor on the drives themselves.
As has been noted, not having these jumpers properly connected will result in the internal fans running at high speed. While “shorting” the sensor as described above may reduce the speed somewhat, I would NOT recommend that method.
We are working on a solution that will work for any model drive you wish to install, but until that is available, the recommended upgrade path would be to a drive by the same manufacturer (Seagate to Seagate, WD to WD).
You followed that path, and by hooking up the cable properly, you should be fine.
Thursday, 19. November 2009
Basically, Apple hasn’t changed the way it reads temperature data from the optical/hard drives. The old way uses a thermistor that now is located into the hard drive itself. If you get one of the old thermal sensor cables and attach it to the logic board will do the same job, try to use same holder and the foam cover for the thermistor when possible.
Thursday, 19. November 2009
Looking forward to a solution while suffering the fan noise!