I've thinking to upgrade my iMac late 2009 with an SSD. Its has a SATA II port and now uses a HD Hitachi 7200rpm. In your opinions, if I'll upgrade, I can see an increase of performance or not? In my project i've thinking to put SSD (250GB) in HD slot and buy an external case for HD in order to store photos and other big files.

Surfing online I've found some forums talk about temperature sensor on HD. I didn't understand which problem there are with this component. Can you explain me if there are problems?

3 Answers 3


Here are some points from my Upgrade of my old iMac (late 2009, Model 10,1, #A1312)

  1. You can expect a significant Performance increase when starting Apps or saving Data, but overall-performance is depends on you RAM size too. If you are working with Photoshop f.e. you should def. have more than 8GB (on 10.10) - the more the better.

  2. You will encounter Problems with the Heat-Sensor. Apple uses a non-standard 3-Pin on the Hitachi HD to access the Heat-Sensor build into the Drive. Other HD or SSD will not have that, so you cannot connect the Heat-Sensor to the Mainboard. The result: the OS will turn up the Fan speed to a maximum, which is annoyingly loud. You can counter that effect with an additional Software to control the Fan speed, f.e. 'HDD-Fan Control' or 'iStat-Menu‘ and others.

  3. In order to fasten the SSD, usually in a 2,5" Format, into the internal 3,5-Slot of the iMac you need a Frame for the SSD. Annoyingly some of the Frames have Screw-Slots in which the Apple Srews do not fit. You should read the excellent visual Tutorial from iFixit for replacing the HDD (Link is for my Model, check your Model before attempting to follow it).

Conclusion: even though it's a PITA, i never regretted doing it.

  • I would add that not all SSD drives are compatible. I just spent the weekend trying to make a Kingston HyperX work with the same iMac model without success.
    – chris
    Feb 20, 2017 at 15:00

I have an iMac late 2009 (21.5") and just replaced the HDD by a Crucial SSD - MX200 with 500 GB. The instalation was easy because the connectors just fitted without issues. I had an bay bracked from Sabrent (model BK-HDDH) that makes very easy to fit. It will also work if you use a double sided tape to fix the SSD in place. I use the app SSD Fan Control to reduce the fan speed and it works like charm.

Very happy with the result as all the operations are now much faster than before. My next objective is to move the SSD to the optical bay and put an HDD back but I am still looking for an nice adapter for the slimline SATA conector.

  • Note that "The optical drive SATA port is only SATA I (1.5 Gb/s) unlike the HD's SATA port which is SATA II (3.0 Gb/s). The problem is the Platform Controller Hub chip used in this system." (as danj says over on ifitix.com)
    – DavidJ
    Feb 21, 2016 at 17:21

your idea is charming, but does not work with your system. What you can do is to add a ssd and merge it with the hd into a fusion drive using Apples on-board tool residing within the disk utility. If you are running Yosemite it will be o. k to just start. if you are running Mavericks and willing to upgrade to Yosemite, DO THIS PRIOR ANY HARDWARE CONFIGURATION CHANGE. Built up the Fusion Drive afterwards! There are two options. 1. Add the ssd atop the hd using a dedicated interface OR 2. Substitute the optical drive with a ssd. (Blame one if I am wrong, but a substitution of the hd a primary boot disk is possible with newer iMacs) I did it the second way because the optical drive was gone on my Mavericks ran mind-blasting fast with the fusion drive. After upgrading to Yosemite it now is slowed somewhat especially while shutting down. I did not had the time to rebuilt the fusion drive directly upon Yosemite but will do it! The best description, including the spare parts and everything else you need, you can find at ifixit.com

Hope that helps tom

  • the OP didn't ask how to make a fusion drive, merely swap out an HD for a new SSD. EveryMac covers how to upgrade, including links to ifixit - everymac.com/systems/apple/imac/imac-aluminum-faq/…
    – Tetsujin
    Nov 15, 2014 at 11:29
  • that might partially right, but many of our clients DO appreciate hints, especially when those are helping to avoid problems
    – tomTom
    Nov 15, 2014 at 13:01
  • ... and if you would have digged a little bit deeper, you would have found out, that you can't replace (=substitue!) a HD with a SSD on these iMacs ...
    – tomTom
    Nov 15, 2014 at 13:04
  • You can, you just need to figure out how to deal with the temp sensor. btw, none of this arguing is making your answer any better.
    – Tetsujin
    Nov 15, 2014 at 13:06
  • So, you suggest me to insert SSD in DVD-slot? Do you think this solution is better? Nov 16, 2014 at 0:22

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