The Aluminium iMac ranges and their hard drives (2011 HD Problem Resolved)

The first generation of iMac was first released back in 1998. This machine, as odd as it may seem, was an innovation of its time. With its built in CRT display and colour synced bodies and accessories, it was a hard act to follow for Apple.

Apples next creation surpassed the iMac G3 by a mile and, in my books, is still the most aesthetically pleasing mac to date. With its flat screen LCD, and the chrome-polished arm, the feather touch angling display was an absolute marvel. First released in 2002, the iMac G4 was sadly discontinued a year later because it was too expensive to manufacture on a large scale.

The next generation of iMac would change the way an all-in-one computer would be viewed for a long time to come. The iMac G5 was first introduced in 2004 and was given a hardware update twice through its short 1 year of being manufactured, firstly with an ambient light sensor in early 2005, then in late 2005 with a built in iSight camera. Although it had its flaws, this model became the basis for the design of many iMacs to come.

The casing didn’t take much of a change when the iMac went intel in early 2006 (besides the machine being built in the reverse order to the G5, as the G5 was built from the LCD backwards with a removable rear panel to access the internal circuitry… with the exception of the iSight model of G5 that is. But the White intel iMac was built from the back to the front, with the LCD and front bezel being the last stage in its construction), but the intel chip dramatically changed the way in which Macs were used. The dramatic speed increase was the first noticeable difference, that’s for sure. As for the partition on the internal hard drives changing from an Apple Partition Map to a GUID partition presenting a problem when upgrading or swapping macs, this was overcome by the introduction of the Migration Assistant years prior. All in all, the intel iMac was a fabulous piece of kit, even in this day and age.

The next generation to follow the white Intel iMac was the first aluminium iMac in 2007. This was another hardware upgrade of substantial measures. Not only was it now encased in a beautifully designed aluminium body, but it was also more powerful with better built in graphics to boot! What more could you ask for?

A hard act to follow you might say? Not for the likes of Apple… The release of the next generation of Aluminium iMac was not as overt as the previous change from white to aluminium, but for the keen eyed among you, the casing design was still improved in many ways. Along with this generational upgrade in Late 2009 came still further hardware upgrades in processor speed, graphics card capability and, well, overall awesomeness.

Now each iMac was not without its flaws… The G3s were prone to fry their CRT displays, while the G4s often blew out their internal power supplies or backlight tubes (in the LCD panel). The G5s had a notorious problem with the logic board capacitors swelling and leaking, which usually caused a graphics fault or kernel panic of some kind, and the white Intel iMacs often blew their internal power supplies. The 24” 2008 Aluminium iMacs NVidia 8800 graphics card usually failed due to a de-flux of the solder used on the main chip… Need I go on?

Needless to say, each generation was easy enough to upgrade or repair if one had the need or the capacity to do so. Although most of the components in these machine were pretty minimalistic, things such as the ram, hard drives and in later cases, the graphics card were parts that could be changed without having to remortgage the house, or sell a kidney on the black market… Or was it…

The first instance it was apparent that there was a limitation in the way in which the iMacs were being configured was in Late 2009 when the second revision of Aluminium iMac was released. Each model before this used an external thermal sensor (attached to the surface of the drive) in order to regulate the internal temperature of the machine. The data is then sent to the main logic board, and the fan RPM speed is adjusted accordingly. The later generations of Aluminium iMac have 16 internal sensors, both ambient and surface temperature sensors. With the 2009 and 2010 generations of 21.5” and 27” iMacs they still used a sensor cable, but instead of using an external surface temperature sensor, they started using the internal SMART disk to regulate the temperature of the drive. This made it difficult to upgrade or change hard drives in these models because each manufacturer uses a different connection on their drives, so if you changed manufacturers, you’d also have to change the thermal sensor cable to match the replacement drive… This limited the possible upgrade choices, as Apple only outsourced to 4 hard drive manufacturers when these machines were made (Samsung, Western Digital, Hitachi and Seagate), so the likes of Toshiba or other such brands was out of the question if you didn’t want to use an application to override the SMART disk temperature reading. The other complication in this frustrating dilemma is that only certain hard drive firmware revisions will work, even if you were to use the same manufacturer that was previously fitted to your machine. Due to the lack of any information on what revisions were compatible, it often turned into a game of russian roulette when trying to find one that would work. It wouldn’t cause any damage to the machine to try different drives, but not everyone has access to 100 different drives of varying capacities and ages to see if they register with the machine. The only other option in these ranges was to fit a hard drive sensor jumper cable to the sensor port of the logic board. This would overcome the issue of the fans spinning up at full speed, but it would not help if the machine or drive were being pushed hard. These jumper cables were designed for when an SSD was being fitted in the second hard drive bay and the primary 3.5” hard drive was being removed (this is possible with the 2010 model 27”, as well as the 2011 27” and the 21.5” Early 2011 machines, but in a slightly different way for each). All it does it bypasses the sensor and the fan will spin at idle speed (1200RPMs) and will not adjust when the machine gets hotter… this option is not advisable in most cases.

This is what led me to the discovery of an external thermal sensor cable that works with these two generations of iMacs. This cable is used on the LCD panel of the 27” 2009 and 2010 models, but has the same connector as the hard drive sensor cable and operates in the same range as the SMART disk does, so functions as a great alternative in these generations of 21.5” and 27” 09/10 machines. This allows one to replace the internal hard drive with any industry standard drive without any sensor problems. The part number is 593-1029. (http://www.thebookyard.com/advanced_search_result.php?keywords=593-1029)

The problem with the 2011 iMacs was even more aggravating, as they stopped using the separate sensor cables to communicate to the SMART disk of the drive, so this meant there was no longer a port on the logic board for the sensor to work with, and they started using the SATA power cable to transfer the data… What a pain!

After trying many, many drives and not finding any firmware revisions that worked without causing the fans to kick up to full RPMs, I decided it was time to see if anyone else had a fix for this problem. Much to my dismay, all but one company I contacted had started coming up with a hardware solution to this problem. I for one wasn’t a fan of potentially having to spend £300+ for a replacement hard drive from Apple if my internal drive were to fail, considering you can pick up a 2TB 3.5” drive for around £75 now-a-days… The solution of using software to control the hard drive fan was another option, but the idea of relying on an application to keep my machine cool wasn’t what I would call a long-term solution for a brand new mac. If anything, it would work as a stopgap until a real solution was made at a later date. Needless to say, after 6 months of waiting for this hardware solution to be manufactured by this company, I had decided I’d had enough. Having to constantly turn customers away for hard drive upgrades or replacements because we didn’t have a solution was beginning to get to me. That’s why I decided to come up with my own solution to the problem.

I’ll break it down a bit, but keeping it brief to prevent any doziness to you readers at the technical stage, as it can sometimes be a bit boring. (but this is the part I enjoy the most)

First it was important to figure out which data tracts were sending the thermal sensor details from the drive to the mac. Then I had the fun job of dissecting the cable and diverting the cable away from the hard drive… the next stage would be to find a sensor that works at the same frequency as the internal SMART disk. This didn’t prove to be very difficult. So after finding the details that I needed, I then ordered a batch of the sensors I needed from a supplier and made a few of the cables to test.

Needless to say, the solution worked like a charm! With a CPU testing app running, the fans all operated at the same rates as they did with the original cables and drives connected. (I’ve tested this on a number of different occasions, one of which I left it running with a CPU test going for nearly a week and it was all reading as it should)

Having established that the solution worked, my next task is to find a way of creating not just a cable, as the cable attaches to the underside of the main logic board, so can be a bit fiddly to fit, but to come up with an adapter for the cable so the logic board doesn’t need to be handled at all. It would simply entail unplugging the hard drives power cable, plugging in the adapter and sticking the sensor to the outside of the drive, and then away you go.

The universal cable solution is now being sold through the website, but the adapter solution hasn’t been as easy to sort out. (its proving difficult to find an adapter that isn’t for both the power and data of the drive, or isn’t cut down to only 4 cables in the middle instead of the full 15) But hopefully it shouldn’t be too far down the line. (http://www.thebookyard.com/product.php?products_id=10085)

Let me know your thoughts, and I hope you’ll drop by our web store if you have any service spare needs!