JRPGfan on 15 August 2018
The reason they use a single chip solution (a apu) is because its cheaper, and has a tiny bit of power saveings in it.
Going with a amd/intel cpu + nvidia gpu on a 2nd chip, will be more expensive to produce.
Also MS put all that work into makeing their games backwards compatible, useing a AMD x86 cpu..... they are not going to stop useing x86 now.
So they would have to get a x86 intel or amd cpu (a tegra Arm cpu just isnt enough, and would break their Backwards compatability).
I think it highly unlikely they dont use AMD next gen as well, for both cpu+gpu.
