Peter Cohen, writing for iMore:
The second and third-generation Apple TV runs a variant of iOS, and the new Apple TV 7.0 software is the first release based on iOS 8. iOS 8’s minimum system requirements exclude the original iPhone 4, which uses the same microprocessor as the second-gen Apple TV.
I’ve had my second-generation Apple TV in the living room since I bought it years ago. When I purchased an additional Apple TV it ended up in the bedroom so that I wouldn’t have to uproot the living room’s media setup and move it (because I’m lazy sometimes). That third-generation Apple TV remained in the bedroom until last night when I made the swap.
I knew that at some point I was going to have to swap the two Apple TVs because Apple would start leaving features out of updates for the second-generation model. And, that update came last week.