How backwards combatable will the PS5 and Xbox Series X be?

Xbox Series X will be compatible with games from original xbox, xbox 360, and xbox one.

I think xbox series X it will let you use accessories from xbox 360 and xbox one too.

Depends on the money; doesn't such?

I guess x box series x will be compatible with x box one x or s.  

I don't know the quantity of games but I do know the PS4/XB1 consoles and the PS5/XB1X consoles both use x86-64 processors, and both Generations will use CPU/GPU co-processors designed by Advanced Micro Devices. 

It's really up to the studios to optimize the games for the new consoles. 

The consoles from the PS1, PS2, and PS3 Generations didn't use x86-64 processors so if those games weren't optimized for the PS4 then they probably won't be optimized for the PS5. 

Sony has said that the PS5 will be backward compatible with select PS4 games. Initially this will be with 100 of the most popular titles, expanding over time.

Xbox has said that the Xbox Series X will play all games that play on the Xbox One. That includes all native Xbox One games as well as whatever 360 and original Xbox games that were made backward compatible on the Xbox One.

The Xbox Series X is closer to being a new version of an existing console, while the PS5 is closer to being a whole new console.

Ps5 will be able to play most ps4 games. At launch, it should be able to play the 100 most played ps4 games. 

Series x will be backward compatible to play Xbox, Xbox 360, and Xbox 1 games. 

I don’t think it will be 100% bc but they should play most of the more popular games. 

any game studio that is owned by the parent company will only produce games for their respective consoles