From the '11 model forward Apple uses custom firmware within the HD to allow the internal thermal sensor (note: not all drives have this sensor) to be used as part of its SMC services which in turn controls the RPM's of the fan or fans of the system. If you try using an older non-compliant drive the fans will ramp up as SMC services will think the sensor within the HD is defective. Over time the fans will wear out and the system will be very noisy compared to what it should sound like. Heres a collection of good write-ups from OWC that describes the issue: [http://blog.macsales.com/10146-apple-further-restricts-upgrade-options-on-new-imacs|Apple Further Restricts Upgrade Options on New iMacs] and [http://blog.macsales.com/10206-further-explained-apples-imac-2011-model-hard-drive-restrictions|Apple’s iMac 2011 Model Hard Drive ‘Restrictions’] and [http://blog.macsales.com/16878-imac-hard-drive-upgradeability-expanded|iMac Hard Drive Upgradeability Expanded!]
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OWC created a special cable so people could put in noncompliant HD's into the '11 system [http://eshop.macsales.com/Search/Search.cfm?Ntk=Primary&Ns=P_Popularity%7c1&Ne=5000&N=7898&Ntt=|'11 Upgrade kit] at the same time Apple was also working with the JEDEC standards group which over see's the SMART HD standard. While it took quite a bit of time Apple was able to get the group to alter the standard so the thermal sensor with in the HD could be accessed in a common method and not inter fear with the performance the the drive (which was why Apple needed to go with custom firmware at the beginning). Now HD's that comply with the updated standard no longer need the OWC cable and have the newer SMART services within their firmware.
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OWC created a special cable so people could put in noncompliant HD's into the '11 system [http://eshop.macsales.com/Search/Search.cfm?Ntk=Primary&Ns=P_Popularity%7c1&Ne=5000&N=7898&Ntt=|'11 Upgrade kit] at the same time Apple was also working with the JEDEC standards group which over see's the SMART HD standard. While it took quite a bit of time Apple was able to get the group to alter the standard so the thermal sensor with in the HD could be accessed in a common method and not interfere with the performance the the drive (which was why Apple needed to go with custom firmware at the beginning). Now HD's that comply with the updated standard no longer need the OWC cable and have the newer SMART services within their firmware.
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If you look at the HD's package you should see an Apple logo on it which is the only clue that I know of. The reason you don't see anything other than that is the drive vendors still have a lot of noncompliant drives out there and they have also being going though a bit of market collapse and contraction (being focused on survival). I also suspect Apple may also be asking for a bit of money for the drives they certify as workable.
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If you look at the HD's package you should see an Apple logo on it which is the only clue that I know of. The reason you don't see anything other than that is the drive vendors still have a lot of noncompliant drives out there and they have also being going though a bit of a market collapse and contraction (being more focused on survival). I also suspect Apple may also be asking for a bit of money for the drives they certify as workable.
In the end you need to be smart shopper on what you buy.
westly197 - Well, Yes & No here ...
From the '11 model forward Apple uses custom firmware within the HD to allow the internal thermal sensor (note: not all drives have this sensor) to be used as part of its SMC services which in turn controls the RPM's of the fan or fans of the system. If you try using an older non-compliant drive the fans will ramp up as SMC services will think the sensor within the HD is defective. Over time the fans will wear out and the system will be very noisy compared to what it should sound like. Heres a collection of good write-ups from OWC that describes the issue: [http://blog.macsales.com/10146-apple-further-restricts-upgrade-options-on-new-imacs|Apple Further Restricts Upgrade Options on New iMacs] and [http://blog.macsales.com/10206-further-explained-apples-imac-2011-model-hard-drive-restrictions|Apple’s iMac 2011 Model Hard Drive ‘Restrictions’] and [http://blog.macsales.com/16878-imac-hard-drive-upgradeability-expanded|iMac Hard Drive Upgradeability Expanded!]
OWC created a special cable so people could put in noncompliant HD's into the '11 system [http://eshop.macsales.com/Search/Search.cfm?Ntk=Primary&Ns=P_Popularity%7c1&Ne=5000&N=7898&Ntt=|'11 Upgrade kit] at the same time Apple was also working with the JEDEC standards group which over see's the SMART HD standard. While it took quite a bit of time Apple was able to get the group to alter the standard so the thermal sensor with in the HD could be accessed in a common method and not inter fear with the performance the the drive (which was why Apple needed to go with custom firmware at the beginning). Now HD's that comply with the updated standard no longer need the OWC cable and have the newer SMART services within their firmware.
If you look at the HD's package you should see an Apple logo on it which is the only clue that I know of. The reason you don't see anything other than that is the drive vendors still have a lot of noncompliant drives out there and they have also being going though a bit of market collapse and contraction (being focused on survival). I also suspect Apple may also be asking for a bit of money for the drives they certify as workable.
In the end you need to be smart shopper on what you buy.