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Hi My hdd is broken so I have to install a new one. Is it possible to install an SSD, and if it is, how is it done and which brand is optimal? Best regards from Sweden! Thomas

Thomas - Heres the guide to gain access to the HD: iFixIt HD Guide If you are not using your optical drive, consider replacing it with the SSD instead. Here’s the guide to take the optical drive out: iFixIt Optical drive guide. In either case you’ll need a 3.5 to 2.5 bracket (depending on which way you go you’ll need different bracket types) and in the case of the optical drive the addition of a optical to HD enclosure Optical to HD SATA enclosure I would strongly recommend getting a Firewire (if you can still find one, it’s getting hard) or USB HD enclosure to house your old HD as a backup drive and using it to prep your SSD. Or use this kit: Universal Drive Adaptor to prep the SSD before you install it. And lastly, the SSD you get must be able to run at SATA II specs

Yes you can depending on the model number. I managed to replace my existing factory fitted HD with a SanDisk 256GB Extreme II drive on my iMac 27" 2374 model. Replacing the hard drive removes the internal HD thermal sensor which is needed by the iMac and a lack of this sensor will cause the fan speeds to constantly run at maximum. To prevent the iMac spinning its fan’s constantly at full speed some people have used software to override this and there is another workaround! If you have a spare thermal 2pin sensor such as one off an older iMac’s optical drive unit (or one purchased online) then you can use this. Carefully plug this into the HD thermal sensor plug (careful not to damage the connector socket) and fix the replacement sensor onto your SSD with sticky tape. I have done this procedure and confirms this works. The iMac is fooled! My iMac is 10 times faster running an SSD! and this procedure allows you to maintain your optical drive unit.

Yes - however it is an advanced DIY. Be certain you have the proper tools (every DIY job is easier when you use the right tools). ID your Mac to find the complete guide. If this Answer is helpful please remember to return and mark it Accepted.

If you are really good, you can fuse the SSD and the HDD to form a Fusion Drive. There are several articles online, one particularly good one by MacWorld. This will combine the SSD and HDD into one logical volume. OS X is smart enough to put the OS and your most frequently used files on the SSD, giving you the speed, and putting the large files on the HDD. This gives you speed without sacrificing size.

If you have USB 3 and/or Thunderbolt you can use an external SSD. I just did that using a Sandisk SSD and Carbon Copy Cloner. Very straightforward and works a treat in terms of speed improvement. Not worth it with USB 2.0 however, which is too slow.

Already SSD was replaced for 21 inch iMac , but without HDD sensor, am using Fan control apps (TG Pro ) to control the speed of fan, i don’t know it will create any issues for iMac