I don't think it's a hardware issue but one of software. The original Xbox ran on a modified NT kernel with some pretty specific DirectX instructions. It was also released 15 years ago. Since both the Xbox and Xbox One are basically PCs, think about it this way: how many 15 year old games work on a modern system without any sort of tweaking? Even GOG has to do a lot of work to resurrect some of our favorite games of the past and sometimes they don't always work perfectly or even well (Interstate '76, for example).
Also, remember that all Xbox Ones recently received the system update that updated them to the Win10 codebase. So they're on DX11 and DX12 now. The original used DirectX 8.1 and was not capable of being updated by design.
Some, if not most, of the features of DirectX 9 are deprecated now and the ones that do work are done via emulation in DX11/12. That's hard enough. Going from a static, ancient 8.1 codebase to the modern codebase is a non-trivial underaking. I give them credit for trying it in the first place.
"No matter where you go, there you are." Buckaroo Banzai
There are two types of computer users: Masochists and Linux users.
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