So, after much soul-searching I decided to attempt a DIY installation of a Corsair Force 240GB SSD in my brand new 27" i7 iMac. I couldn't quite bring myself to pay extra for Apple's SSD option, a Toshiba drive which is not only considerably slower than the Corsair Force when new, but also suffers from significant performance degradation over time. Given that OS X doesn't support TRIM for the moment, a Sandforce drive like the Corsair Force is a far better option, an opinion shared by Anandtech.
The installation was a success, but I must stress that it's not for the faint of heart! Replacing the built-in Hard Disk would be considerably easier than installing an additional SSD, but if you know what you're doing and want to give it a go, perhaps these tips will help. You should also consult the iFixit teardown of last year's iMac for details of screw locations and instructions for removing the display cables, which must be done with great care.
- As described in this OWC blog post, you will need a left-angled SATA cable (8" is enough) and a SATA Power Y-cable (6" is plenty). You should be able to buy both of these cables on eBay for just a few dollars. (Ignore the molex power cables, you need a power splitter with one male SATA power connector on one end and two female SATA power connectors on the other end.)
- There's no need to improvise any kind of drive cage or attachment mechanism to keep the drive in place. It's such a snug fit that it can't possibly go anywhere.
- You'll inevitably be touching the innards of your iMac at some point, so make sure you ground yourself somehow to avoid the possibility of static discharge killing a sensitive component.
- You can remove the glass panel on the front of the iMac with your fingernails alone. No need for suction cups! This is easiest done while the iMac is standing upright. The glass panel won't fall out because of the way it interlocks with the case at the bottom edge, just ease the top edge forward and then lift it upwards to free it.
- Once the display and HD are out of the way, you'll need to remove eight screws to loosen the motherboard enough to lift it forward and connect the left-angled SATA cable to the spare slot on the back of the motherboard. You'll have to use your head to work out which screws to remove, it's not entirely obvious. There's no need to remove any screws covered with warranty stickers.
- As mentioned, the space for the SSD is very tight. You'll have to slide it into place behind the wires that are there so that it's resting against the very back of the machine, and connect the SATA data and power cables once it's in place.
- When you reconnect the HD, make sure you don't forget about the temperature jumper cable!
- You should invest in some canned air to blow away dust before replacing the glass panel at the end of the installation.
That's it. A bit fiddly but well worthwhile in the end. I haven't had much chance to test the drive yet, but on a default installation of OS X I went to Applications -> Select All -> Open ... and it took ~2 seconds to open everything no exaggeration. It shocked me, and I was expecting it to be fast.
The installation was a success, but I must stress that it's not for the faint of heart! Replacing the built-in Hard Disk would be considerably easier than installing an additional SSD, but if you know what you're doing and want to give it a go, perhaps these tips will help. You should also consult the iFixit teardown of last year's iMac for details of screw locations and instructions for removing the display cables, which must be done with great care.
- As described in this OWC blog post, you will need a left-angled SATA cable (8" is enough) and a SATA Power Y-cable (6" is plenty). You should be able to buy both of these cables on eBay for just a few dollars. (Ignore the molex power cables, you need a power splitter with one male SATA power connector on one end and two female SATA power connectors on the other end.)
- There's no need to improvise any kind of drive cage or attachment mechanism to keep the drive in place. It's such a snug fit that it can't possibly go anywhere.
- You'll inevitably be touching the innards of your iMac at some point, so make sure you ground yourself somehow to avoid the possibility of static discharge killing a sensitive component.
- You can remove the glass panel on the front of the iMac with your fingernails alone. No need for suction cups! This is easiest done while the iMac is standing upright. The glass panel won't fall out because of the way it interlocks with the case at the bottom edge, just ease the top edge forward and then lift it upwards to free it.
- Once the display and HD are out of the way, you'll need to remove eight screws to loosen the motherboard enough to lift it forward and connect the left-angled SATA cable to the spare slot on the back of the motherboard. You'll have to use your head to work out which screws to remove, it's not entirely obvious. There's no need to remove any screws covered with warranty stickers.
- As mentioned, the space for the SSD is very tight. You'll have to slide it into place behind the wires that are there so that it's resting against the very back of the machine, and connect the SATA data and power cables once it's in place.
- When you reconnect the HD, make sure you don't forget about the temperature jumper cable!
- You should invest in some canned air to blow away dust before replacing the glass panel at the end of the installation.
That's it. A bit fiddly but well worthwhile in the end. I haven't had much chance to test the drive yet, but on a default installation of OS X I went to Applications -> Select All -> Open ... and it took ~2 seconds to open everything no exaggeration. It shocked me, and I was expecting it to be fast.
Anyway, I've bought one of each already but one of them is a bit slimmer (the one pictured above) so if it's that one it's nice. 
