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Aluminum iMac Q&A - Updated April 19, 2012

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How do you upgrade the hard drive in the "Late 2009," "Mid-2010," "Mid-2011" and "Late 2011" (21.5-Inch and 27-Inch) Aluminum iMac models? What type of storage do they support? Is it even possible to upgrade these models?

Please note that this Q&A covers Aluminum iMac models with 21.5-Inch and 27-Inch displays. For earlier 20-Inch and 24-Inch models, please see "How do you upgrade the hard drive in the 'Original,' 'Early 2008' and 'Early 2009' (20-Inch and 24-Inch) Aluminum iMac models? What type of hard drive do they support? Can you swap the hard drive for an SSD?"

Apple considers the memory in the "Late 2009," "Mid-2010" and "Mid-2011" Aluminum iMac models -- all Aluminum iMacs with 21.5-Inch and 27-Inch displays -- to be a "customer installable part" but the hard drive is not intended to be upgraded by end users. Upgrading the memory is extremely easy -- there is a small removable "door" on the bottom of each system for this purpose -- but upgrading the hard drive requires one to gingerly remove the display and effectively disassemble the entire computer.

Identification Help

If you're not sure which 21.5-Inch or 27-Inch Aluminum iMac you have, these models can be most readily identified externally via EMC number (located inconveniently under the "foot" supporting the computer). More conveniently, they can be identified in software by model identifier.

These models also can be identified by their serial number using's Ultimate Mac Lookup feature.

Supported Hard Drive & SSD Types

All "Late 2009" iMac models -- the iMac "Core 2 Duo" 3.06 21.5", "Core 2 Duo" 3.06 27", and "Core i5" 2.66 27" -- and all "Mid-2010" models -- the iMac "Core i3" 3.06 21.5", "Core i3" 3.2 21.5", "Core i3" 3.2 27" and "Core i5" 2.8 27" -- have a 3 Gb/s SATA 2.0 connector for a 3.5" hard drive. The 27-Inch "Mid-2010" models -- the iMac "Core i3" 3.2 27" and "Core i5" 2.8 27" -- also have an extra 3 Gb/s SATA 2.0 connector and power for the optional 2.5" SSD (in addition to 3 Gb/s Serial ATA 2.0 connectors for the hard drive and optical drive).

The "Mid-2011" iMac models -- the iMac "Core i5" 2.5 21.5", "Core i5" 2.7 21.5", iMac "Core i5" 2.7 27" and "Core i5" 3.1 27" -- all support a single 3.5" hard drive and a second 2.5" SSD. As shipped, both the hard drive bay and SSD bay provided support for the 3 Gb/s Serial ATA 2.0 standard. However, as first discovered by site sponsor Other World Computing, the iMac EFI Update 1.6, released two days later, quietly provided faster 6 Gb/s Serial ATA 3.0 support for both of these connectors (but not the optical drive connector).

Although no official information is available, it is assumed that the education-only iMac "Core i3" 3.1 21.5-Inch (Late 2011) supports at least a single 3.5" hard drive using the 6 Gb/s Serial ATA 3.0 standard. However, it is possible that it is limited in EFI to 3 Gb/s. It is assumed to not support a 2.5" SSD simultaneously with an internal hard drive, but this also is speculative. If you have additional information, please share.

Hard Drive Upgrade Obstacles

Unfortunately, taking the computer apart -- which is challenging enough -- is not the only obstacle to upgrading the hard drive in these Macs.

OWC also discovered that the "Late 2009" -- and subsequently introduced "Mid-2010" -- models use a "connector that seems to use the drive's internal sensors" rather than an external sensor like earlier 20-Inch and 24-Inch Aluminum iMac models.

This means that the most straightforward way to upgrade the hard drive is to "replace the drive with another model from the same manufacturer that [OWC or another third-party has] confirmed works properly with this thermal sensor cable". OWC provides a list of compatible drives. Readers have shared reports that taping an external temperature sensor to a hard drive or SSD that does not have an internal sensor will work in these models, but this method could be risky when data is important.

As again found by OWC, if an SSD is not installed at the time of purchase in the 27-Inch "Mid-2010" models -- the iMac "Core i3" 3.2 27" and "Core i5" 2.8 27" -- the connector cables and mounting bracket are not present. It still is possible to install a 2.5" SSD in addition to the hard drive if an SSD is not installed initially, but one will have to find a way to mount it place. It also is worth noting that if a 27-Inch "Mid-2010" iMac is configured with an SSD, but without a hard drive, the hard drive temperature sensor is not present either.

For the "Mid-2011" models, OWC once more touched off a firestorm across the blogosphere by reporting that Apple has gone even further in the company's effort to restrict hard drive upgrade options:

For the main 3.5" SATA hard drive bay in the new 2011 machines, Apple has altered the SATA power connector itself from a standard 4-wire power configuration to a 7-wire configuration. 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 machines 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). . .
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.

Needless to say, this obstacle to upgrade the hard drive was quite disappointing.

Hard Drive Upgrade Solutions

Stating that the "Apple-branded main hard drive cannot be moved, removed, or replaced" in the 2011 iMac models may have been a bit pessimistic, and perhaps should have been qualified by "officially" and "easily."

In response to feedback, OWC provided a follow up post noting detailed testing methodology and HDD Fan Control as one unofficial, potential option.

The HDD Fan Control software application cleverly:

Installs as a preference pane to allow you to adjust the speed of the internal hard drive fan and to set a temperature to speed relationship, temperature of the drive is obtained using S.M.A.R.T. so an Apple temperature sensor is not required [in any 21.5-Inch or 27-Inch Aluminum iMac].

A hardware-based option, as first discovered by HardMac, may be forthcoming as well. Gravis, which long-term readers may know from all the way back to their Mac clone days, has developed a "cBreeze" component "which will be able to replace the sensor inside the hard drive" rather than "short-circuiting some [specific thermal-related] pins in the power supply of the hard drive," which also may be a quick-and-dirty solution, albeit one with unknown long-term consequences.

As of the date last updated (see top), this hardware component doesn't seem to be available for online purchase, but the software option still is a good one for those interested in replacing the primary hard drive.

Hard Drive & SSD Installation Instructions

This is a difficult upgrade. It is recommended that a professional upgrade the hard drive or even install an SSD in the secondary drive bay in the "Mid-2011" 21.5-Inch or 27-Inch models.

However, adventurous and skilled "hacker" types could use hard drive replacement guides from the illustrious iFixit or even disassembly photos from Kodawarisan to take apart these iMac models and access the hard drive. Note that these models have significant "hooks" behind the display and removing the glass is particularly tricky, even when compared to earlier Aluminum iMac models.

For the secondary SSD in the "Mid-2011" 27-Inch models, OWC provides this helpful step-by-step video of the challenging disassembly and upgrade process:

By watching this video, you should have a good idea about whether or not you feel comfortable performing the upgrade yourself or if you would prefer to hire a professional. The overall process is similar, but an OWC video for the "Mid-2011" 21.5-Inch models is forthcoming, too.

Hard Drive Upgrade Conclusion

Ultimately, it is possible to upgrade the hard drive in the 21.5-Inch and 27-Inch Aluminum iMac models or upgrade or install a secondary SSD in the "Mid-2011" 21.5-Inch models and "Mid-2010" and "Mid-2011" 27-Inch models, but just opening the case is a challenge and it is definitely not for the faint of heart.

That it has become even more difficult to upgrade the hard drive in the "Mid-2011" and "Late 2011" iMac models with a layer of software complexity certainly is unfortunate. However, creative hackers no doubt will continue to find ways around whatever limitations are in place whether using software methods, hardware methods, or a combination of the two.

If you have additional information about upgrading the hard drive in any 21.5-Inch or 27-Inch iMac model based on hands-on experience please share. Thank you.

Site sponsor OWC sells hard drives and other upgrades for the Aluminum iMac models (and all other Macs).

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