IMac 21.5” mid-2010 SATA Specification

In the Mid 2011 iMacs (both 21.5" and 27") Apple left enough room for an extra SSD. So if you want to put an SSD inside your iMac you can do that without replacing the DVD drive and/or original hdd. If you're going for an external one you should indeed opt for a SSD with a Thunderbolt connection, otherwise you kinda loose the speed advantage of a SSD.

If you want to separate the OS and application data from your media files, that's entirely possible and there's more than one way to achieve that. Read this and decide for yourself wether it's easy:

• http://www.tuaw.com/2012/01/20/ask-tuaw-how-do-i-setup-a-mac-with-both-an-ssd-and-a-regular-hd/
• http://mattgemmell.com/2011/06/21/using-os-x-with-an-ssd-plus-hdd-setup/

SSDs will only get better and cheaper over time so it can make sense to wait, but since they'll keep getting better and cheaper you could also wait for the rest of your life but SSDs are becoming mainstream now so it is safe to make the jump.

Remember that if you install a SSD in your iMac yourself you will loose your warranty so it may be worth to let an Apple Authorized Service Provider do the upgrade for you. If you insist on doing it yourself you might find the following link useful:

• http://www.ifixit.com/Guide/Installing-iMac-Intel-21-5-Inch-EMC-2428-Dual-Hard-Drive-Kit/6434/1

Good luck!

The iMac Mid-2010 supports DDR3 10666 (from the Apple support site)

The first link is to the correct RAM for that Front Side Bus (FSB) speed The second link is to a slightly quicker set of RAM, but runs on a lower FSB.

The differences between the two are characterised by the two notes above, the FSB speed and the clock timings.

In the first, the FSB speed is higher, but the timings for the RAM are slower. In the second, the slower FSB allows the RAM to work at slightly faster timings.

If you want to know about timings, a search for RAS CAS delay is a good starting point.