ELI5: Why is it so hard for game consoles to include backwards compatibility?

Here's something I wanted to add:

Specifically in the case of the PS4 versus the PS3, their system architectures are much different.

The PS3 used what was called an RSX "reality engine" cell chip that was unique.

The PS4 uses a normal off-the-shelf CPU.

So emulation would be very difficult if not impossible, because the two processors work very differently on a low level. (The emulating processor would have to be much much much faster than the processor being emulated)

The Xbox doesn't have this problem, because the 360 used a normal CPU, and so does the Xbox One, so they kind of.. speak the same language.

A game that ran on the 360 also runs on the One, because they both essentially run Windows. The Xbox One is just like.. a faster computer.

ELI5: It just isn't a good idea.

/r/explainlikeimfive Thread