I'm using an Intel based iMac (Mid-2011 model) 21.5 inch. It comes with a 500GB hard drive (ST3500418AS) and I'd like to replace (not add a new drive by removing the optical disk drive) that drive with an SSD (Samsung 840 EVO-Series 1TB 2.5-Inch SATA III Model #MZ-7TE1T0BW) SSD link below: the ssd itself is 2.5 inch and I'm going to convert that drive to 3.5 inch drive by using a WD icepack which is sold on amazon.com for about $20 usd WD Icepack link below: first I'm going to attach the ssd into the WD icepack and then I'm planning to replace the original HDD that comes with the iMac by installing the SSD. My questions are: 1. Does apple allow 3rd party SSD's for iMac? Do I need any additional cable kit?

Is it enough to change just the drives? (I mean HDD comes with a termal sensor, does the SSD need a termal sensor?) 4. Do I need any software after installing the SSD (if possible) to control iMac's fan speed I heard some people complaining about their fan speeds and the loudness of the fans. First you have a spare SATA port in this model so you don't need to remove your current HD or the optical drive. So you can follow this IFIXIT guide:. Go to Step 46 as you can see you are wedging the second drive (HD or SSD) behind the optical drive. Once you've put the SSD in you can then create a Fusion drive across both your HD and SSD gaining the benefits of each.

If you decide to just replace your HD for a SSD thats fine to. But you'll need to use this special cable:. Frankly, I think the best option here is swapping out your HD for a SSHD (hybrid HD). Here you'll gain the performance of the SSD but the storage capacity of a HD. Here's the Seagate web site: and here is the spec sheet for the SSHD series:. Thanks for the suggestions Dan. Actually I've ordered the stuff (links available) that I'm going to use for the upgrade on my first message.

Do I still need that Thermal Sensor Cable for replacing the original HDD. Because I do not want to use the spinning drive anymore and I don't want to place my SSD under the optical drive (that way it will take about 10 hours for me to disassemble all the parts lol) May I remove the old HDD and replace my new SSD into its place? I mean, will it work that simple? Yes, You can swap out the HD for the SSD. But you'll need the special cable and a standard 2.5' to 3.5' drive adapter frame (you don't need the IcePack frame as the SSD does not get hot like the WD drive the frame was designed for). A standard adapter frame is about $5.00.

Why do you want to go with a straight SSD? The SSHD are very close to the same speed and cost much less for the storage space (the difference is about $300 in your case). If I were you I would return both parts to save the money. The issue here is the way Apple leverages HD's which have an internal temp sensor so the system is able to manage the heat created as the drive is used.

SSD's while they do get warm don't get as hot as HD's and thats the rub here! So to your question you require a sensor and it needs to meet Apples requirements hence you need the OWC cable for a HD to SSD swap. You really can't use the standard SATA/Power cable setup without having to deal with the systems fan management. True, some people easily on created software to override the fans. Over time its been proven as not a wise choice as the systems lifespan is greatly reduced as the system can't dynamically adjust the fans to manage the ups and downs of heat buildup. I won't put a straight SSD in the newer systems as the primary drive without the cable or get a SSHD that has the builtin sensor and gives you similar performance of a SSD.

How about going with a SSHD (hybrid drive)? It will give you the zip you're looking for with the SSD and still offer the deeper storage a HD offers. Unlike the SSD solution (swapping out the HD for it) the SSHD has the needed built-in thermal sensor (you won't need the OWC cable). Review this:.

Your other option here in the '11 iMac is setting up a dual drive here you leave the HD alone and add in the SSD using the spare SATA & power connections on the logic board. Review this IFIXIT guide:. Indeed my intention is to add a SSD (and keep my current 1To HD). But I still read many comments of people having problem with their fan. So to summarize: - replacement of HD - OWC cable with temperature probe or 'Mac-compatible' drive with any cable - installation of a second drive (SSD) - any SSD + iFixit cable will do the trick Final question: do you know if I can install Windows (bootcamp) on a partition of the SSD if not installed as the primary drive?

I understood the PC are less flexible when it comes to this kind of questions. OK, so you're going dual drive thats fine;- So the SSD with be your primary drive correct? Then you'll install BootCamp and Windows on the SSD (with your Windows Apps) or you'll need to setup a Fusion drive config which is bounding the two drives as one logical drive, letting OS-X manage where the files go.

The problem you'll face here is the side of your SSD may not be big enough if you setup a dual drive setup (each independent of each other) you need to have both OS's (and any other OS) on the SSD with the Apps (OS-X & Windows). For both OS-X & Windows you'll need to leave about 1/3 (no less that 1/4) of the SSD free for temp files, virtual RAM and/or Paging files. A Fusion setup can help here but you're then loosing some of the performance you wanted with the SSD. At that point you'll might as well go with the SSHD. You'll need to do the math on how much space you'll need to buy (the SSD) to make it work for you. Hello Dan, Just so i understand your amazingly thorough post, if I don't want to use the HD drive in my mid 2011 21.5 iMac, do I just follow the instruction provided, adding the SDD drive using the optical thermal sensor from OWC?? My confusion is that your link shows you how to add an SSD drive to make a dual drive with the HD, but when you mention the option of not using the original HD, you use the word 'replace' and then mention the use of the OWC optical thermal sensor.

Am I removing the old HD and replacing it with the new SSD or am I adding the new SSD keeping the old HD,but using just the SSD? Hope that makes sense. Thanks in advance.

I think you got a bit confused here;- The two directions were swap out HD for SSD OR Add SSD. For the swap (replacing your current HD) you'll need the OWC inline thermal sensor as the SSD does not offer the needed interface for the SMC thermal services of the system.

In the case of the Add SSD, no thermal sensor required! OK, now to really confuse you! In addition you can even swap out the optical drive with a special drive carrier to then hold a 3rd drive! This is what I think got you here as you were talking about the optical drives thermal sensor. Here is the older 2010 dual drive setup which you could do 'in addition' to the above but remember, you loose the optical drive which is why I don't do this in this series: Hope it makes sense now!

Lastly, the comment on using a SSHD was if the current HD drive was dead or just undersized. It offers deeper storage (just like a HD) and yet has some zip like a SSD. It offers a cheaper solution and less work than the dual drive config. SSD are great!

Don't get me wrong. But the cost is a killer $$$ when you need more storage and only using a single drive. This is where a 512 GB or 1 TG SSD are just to costly for most. A dual drive setup (HD & SSD) is a good solution!

Here you're using the speed of a smaller SSD for your boot up and then the traditional HD for its deep storage. But wait a sec here. Didn't I just say the same things when describing the SSHD?? Its almost the same thing!

The two differences are the drive deals with where the files go in the SSD cache or on the disk, where here you need to manage it across the two physical drives. But wait a sec here. Isn't an Apple Fusion Drive doing that! And you could convert the two drives into it. And the second is the size of the SSD cache is fixed on the SSHD drive. As I sent this I realized my mistake in writing you. I know you recommended the SSHD seagate model, but do you recommend any particular SSD if i went that route?

How do the SSHD work with regards to how much SSD space is set aside for often used files, cache, etc. And how much is HD for deeper storage?

I'm assuming the SSDs are double the speed, but see your point about cost. Costs for SSD have gone down.

I do have a 4 tb external thunderbolt hard drive as well. Sorry for my misunderstanding. Thanks in advance.

I'm sorry as I realize this is an older thread. So I failed to do my due dilligence prior to buying a new SSD for my wife's Mid 2011, 21.5 iMac.

I wanted to know if this is possible. I want to install the SSD in the spare bay behind the optical drive. Prior to doing that was thinking I would clone the HDD to the SSD, then wipe the HDD. This way the iMac runs the OS from the SSD and has another storage drive. It is Mid 2011 model so I do not have much faith the HDD has much life left in her so want to transfer the OS and other valuables off of it. Figure I will use it for nonessential things. Creative cloud for mac. I have a 2 TB Lacie external HDD that I would place anything super important onto.

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Does this plan sound too difficult or is it possible? Technically there is no bay. All you're doing here is mounting the SSD to the case using double sided foam tape. Which more than enough to hold it. I think you've got to complex a process here.

If your HD is still working just down load the OS installer on to the HD, open the system install the SSD. Then run the OS installer and install a fresh copy of the OS on the SSD leveraging your HD. Once done use the Migration Assistant to copy over your Apps to the SSD then go into the system prefs to alter the startup to the SSD. If your HD is getting ruff, you'll need to either install a new drive or transfer the SSD over to the HD location and you'll need to install the OWC in-line thermal sensor to replace the custom in drive sensor. If you have a useless leg it often makes sense to cut it off.

Having a dead drive is similar. It makes little sense leaving it. But we do have a small issue with its internal sensor which the systems SMC services uses, so if you pull the drive the missing sensor creates an issue. If you were to move the SSD over you would still have an issue as the sensor output is not present on the SSD.

Which is why you need the in-line OWC sensor. I do like having a dual drive setup! It allows one to have the SSD being the boot drive & App drive and then leverage the larger HDD as to data drive.

Using an external while important as a backup of your data, is not always the best I/O (speed), FireWire and USB are slower interfaces, Thunderbolt in its 3rd generation is faster than SATA III (6.0 Gb/s) internal I/O your system has. The older generations is almost matching the internal SATA port but its getting hard to find the better drives. Which is why I would go with the internal drive. You may have miss understood me.

I was implying your steps you had outlined as being overly complex needlessly. No need for cloning, Apples Migration Assistant utility is by far better! I installed a 1 TB hybrid drive in my 2009 27' iMac, the reason I did this was so I could remove the sensor off the old 1 TB drive and put it on the new hybrid drive (SSHD). That way the temp sensor does not run the fans at super full speed.

Also at the time I read about SSD's they need to be purged once in a while, maybe not now but 3 years ago I think that was the case. So with the hybrid drive as it needs to it can purge the caching flash part of the drive. In the end the programs and files I use all the time are right there and the stuff I don't use all the time is still in the deeper storage on the HD side, so it starts up quick and programs I use all the time open right up. This seems to work well for me. I have a 2 TB drive on the time machine that I only turn on once in a while.

For many this is a good half step! Back then SSD drives where expensive. Today the price of a 512 GB to 1 TB SSD has dropped to a more realistic price. For many a SSHD hybrid drive does make sense.

If you want still more performance a dual drive setup either as discrete drives (SSD & HDD) or combining them into one logical drive by creating a Fusion Drive may offer a option. Apple finally allowed 3rd party drives to leverage TRIM services within the MacOS.

So now you can go either way having a SSHD swapping out your old HDD, or if you can swing it upgrade the HD and add in a second drive in this case a SSD. If space is not an issue then swapping out the HDD for a SSD also makes sense. That would give you the best performance.

But be careful! You'll need to put in the in-line thermal sensor if you swap out the orginal Apple drive with another drive which does not offer the needed internal thermal sensor connection. I've got a question about some of the information you've posted. Background: I have a mid-2011 21.5' iMac. In Disk Utility, the hard drive (factory-original Seagate ST3500418AS, 500GB) reports S.M.A.R.T. Status as 'failing.'

In researching how to properly replace the HD, I've seen all the discussion (here and elsewhere) about the proprietary temperature sensing firmware etc. That was added in the 2011 iMacs. In your comments above, you mention a couple times that replacing the factory HDD with a SSHD would not require the OWC in-line sensor cable ('get a SSHD that has the builtin sensor and gives you similar performance of a SSD' - 1/6/2015; 'the SSHD has the needed built-in thermal sensor (you won't need the OWC cable)' - 1/6/2015). But then elsewhere, you say that even with an SSHD, you'll still need the OWC in-line sensor cable ('Don't forget you'll need the OWC in-line sensor if you go with the SSHD!'

- 9/16/2017; 'You still need the OWC in-line thermal sensor cable.' - 9/16/2017). I'm not trying to call you out at all.I'm just confused-which is it? Could you clarify for those of us that might be in this situation? Are there any SSHD's that do have a built-in sensor and appropriate firmware, such that no OWC cable is required? If so, do you know which brands/models are suitable? I am trying to avoid buying the OWC cable if possible, given the somewhat steep price for such a small part ($40+).

I would much rather spend that extra money on a larger/faster disk drive that already has a built-in thermal sensor. Thanks in advance! Hi, i have same issue, Beware iMac 27 mid 2011, don't work with samsung 860 EVO (Because samsung use unsupported new controller) also same situation can be with 850 EVO (i didn't check with this series), so optimal for upgrade without any risk will be use 840 EVO series. Symptomatic is next: When you connect 860 EVO (I check it) or 850 EVO (I didn't check it 850 EVO, so info for 850 EVO maybe not correct). You can start from internet recovery but you cannot do fusion drive, for fusion drive you should start from USB recovery, yes you can do fusion drive with 860 EVO or 850 EVO but then when will be recovery from time machine you will se error and time machine is stop, then if you will try install new system to you new fusion formatted disk, you will cannot install, not sierra, not sierra high, maybe el captain will work but you will see many error when install it (6 hours maybe), if you still install some OS don't start to be happy, because will be many errors and white screen. So by the way. If you try to instal os to pure ssd, it's also will be with error.

So conclusion don't use 860 EVO and 850 EVO with iMac 27 mid 2011 (I have core i5 3,1). So your SSD will work with USB 2.0 on your iMac, or need to buy thunderbolt ssd adapter or thunderbolt usb 3.0. I think he is confused;- YES it's NEEDED!

The iMac's all use a thermal sensor on or within the HDD to learn the temp of the drive so SMC services within the system is able to manage the heat. Different series of iMac's have done this differently over the years. The 2011 iMac (either one) leveraged a set of pins (header) the drive makers had. Here the drive makers modified their drives to met Apples needs. So a real Apple drive has this special firmware & connections, any stock drive you buy won't have it setup as Apple is expecting. Here's a bit more: As such your system will not see the needed signal and ramp up the fans going into fail safe mode.

So if you put in a replacement drive (either a HDD or SSD you need to a special cable to add in the needed sensor. This cable is placed in-line with your current HD SATA cable and the thermal sensor is them placed onto the drive. This is the only way I replace HDD's in the 2011 models. Using any other method to override the fans is very risky!

As they tend to either kill the fans or overheat/thermal shock your logic board killing it.