From a quick look at Windows 10X build 20279 (fe_release_10x) on 64-bit Arm:
- No x86(_64) backwards compatibility for UWP apps
Which brings us to the next point…
- Arm 32-bit compatibility is not only there but required, base applications such as the Microsoft Store rely on it.
This also applies to 64-bit Arm Windows desktop SKUs. This issue is not resolved on Windows 10X. Even Microsoft didn’t transition all their in-house apps to 64-bit Arm yet. And that’s 3 years past the Arm 64-bit Windows release.
32-bit Arm compatibility is going away in the hardware very soon. Matterhorn, the successor of the Cortex-A78, is the last chip to have it in hardware on the Cortex-A big core line. Makalu, its successor, drops it.
- No desktop application compatibility… and some special-purpose shims
This issue applies to Windows 10X on x86_64 too. Note however that Microsoft Edge runs outside of the sandbox that every third-party app developer has to go through on Windows 10X, with a compatibility shim.
It would be nice if Microsoft’s own web browser would in the same environment that third-party app developers have to target for the platform.
- Uses a BSP model, like Mobile and IoT Core
You won’t be able to have Windows 10X install media that will be usable everywhere. Windows 10X images are tailored to a given hardware model.
- Every 3rd-party app is sandboxed
The times of just running non-Microsoft signed code outside of the sandbox are gone. It’s to be seen if Microsoft will relax those restrictions for users who don’t want them, if only for tinkering.
- Is branded as Windows, runs within the same form factors as existing Windows devices, but does not have the compatibility that Windows is known for.
We’ll see the results and market acceptance of this product months from now. Windows 10 and Windows 10X are hard to distinguish as names for an unaware observer.